diff --git a/Public/css/output.css b/Public/css/output.css
index 36ea1fd..259c4eb 100644
--- a/Public/css/output.css
+++ b/Public/css/output.css
@@ -5231,6 +5231,9 @@
   .m-1 {
     margin: calc(var(--spacing) * 1);
   }
+  .m-4 {
+    margin: calc(var(--spacing) * 4);
+  }
   .m-6 {
     margin: calc(var(--spacing) * 6);
   }
@@ -5374,6 +5377,9 @@
   .-my-2 {
     margin-block: calc(var(--spacing) * -2);
   }
+  .-my-4 {
+    margin-block: calc(var(--spacing) * -4);
+  }
   .my-1 {
     margin-block: calc(var(--spacing) * 1);
   }
@@ -5646,6 +5652,9 @@
   .mt-1 {
     margin-top: calc(var(--spacing) * 1);
   }
+  .mt-2 {
+    margin-top: calc(var(--spacing) * 2);
+  }
   .mt-4 {
     margin-top: calc(var(--spacing) * 4);
   }
@@ -6604,9 +6613,6 @@
   .max-w-1\/3 {
     max-width: calc(1/3 * 100%);
   }
-  .max-w-\[300px\] {
-    max-width: 300px;
-  }
   .flex-1 {
     flex: 1;
   }
@@ -6812,6 +6818,9 @@
   .flex-col {
     flex-direction: column;
   }
+  .flex-row {
+    flex-direction: row;
+  }
   .flex-wrap {
     flex-wrap: wrap;
   }
@@ -7905,6 +7914,12 @@
   .py-2 {
     padding-block: calc(var(--spacing) * 2);
   }
+  .py-4 {
+    padding-block: calc(var(--spacing) * 4);
+  }
+  .py-6 {
+    padding-block: calc(var(--spacing) * 6);
+  }
   .ps-2 {
     padding-inline-start: calc(var(--spacing) * 2);
   }
@@ -7982,6 +7997,14 @@
     font-size: var(--text-3xl);
     line-height: var(--tw-leading, var(--text-3xl--line-height));
   }
+  .text-4xl {
+    font-size: var(--text-4xl);
+    line-height: var(--tw-leading, var(--text-4xl--line-height));
+  }
+  .text-base {
+    font-size: var(--text-base);
+    line-height: var(--tw-leading, var(--text-base--line-height));
+  }
   .text-lg {
     font-size: var(--text-lg);
     line-height: var(--tw-leading, var(--text-lg--line-height));
diff --git a/Sources/DatabaseClient/TrunkSizes.swift b/Sources/DatabaseClient/TrunkSizes.swift
index d96b4d5..e5c851b 100644
--- a/Sources/DatabaseClient/TrunkSizes.swift
+++ b/Sources/DatabaseClient/TrunkSizes.swift
@@ -11,6 +11,9 @@ extension DatabaseClient {
     public var delete: @Sendable (DuctSizing.TrunkSize.ID) async throws -> Void
     public var fetch: @Sendable (Project.ID) async throws -> [DuctSizing.TrunkSize]
     public var get: @Sendable (DuctSizing.TrunkSize.ID) async throws -> DuctSizing.TrunkSize?
+    public var update:
+      @Sendable (DuctSizing.TrunkSize.ID, DuctSizing.TrunkSize.Update) async throws ->
+        DuctSizing.TrunkSize
   }
 }
 
@@ -82,6 +85,21 @@ extension DatabaseClient.TrunkSizes: TestDependencyKey {
           return nil
         }
         return try await model.toDTO(on: database)
+      },
+      update: { id, updates in
+        guard
+          let model =
+            try await TrunkModel
+            .query(on: database)
+            .with(\.$rooms)
+            .filter(\.$id == id)
+            .first()
+        else {
+          throw NotFoundError()
+        }
+        try updates.validate()
+        try await model.applyUpdates(updates, on: database)
+        return try await model.toDTO(on: database)
       }
     )
   }
@@ -107,7 +125,21 @@ extension DuctSizing.TrunkSize.Create {
       height: height
     )
   }
+}
 
+extension DuctSizing.TrunkSize.Update {
+  func validate() throws(ValidationError) {
+    if let rooms {
+      guard rooms.count > 0 else {
+        throw ValidationError("Trunk size should have associated rooms / registers.")
+      }
+    }
+    if let height {
+      guard height > 0 else {
+        throw ValidationError("Trunk size height should be greater than 0.")
+      }
+    }
+  }
 }
 
 extension DuctSizing.TrunkSize {
@@ -250,4 +282,62 @@ final class TrunkModel: Model, @unchecked Sendable {
     )
 
   }
+
+  func applyUpdates(
+    _ updates: DuctSizing.TrunkSize.Update,
+    on database: any Database
+  ) async throws {
+    if let type = updates.type, type.rawValue != self.type {
+      self.type = type.rawValue
+    }
+    if let height = updates.height, height != self.height {
+      self.height = height
+    }
+    if hasChanges {
+      try await self.save(on: database)
+    }
+
+    guard let updateRooms = updates.rooms else {
+      return
+    }
+
+    // Update rooms.
+    let rooms = try await TrunkRoomModel.query(on: database)
+      .with(\.$room)
+      .filter(\.$trunk.$id == requireID())
+      .all()
+
+    for (roomID, registers) in updateRooms {
+      if let currRoom = rooms.first(where: { $0.$room.id == roomID }) {
+        database.logger.debug("CURRENT ROOM: \(currRoom.room.name)")
+        if registers != currRoom.registers {
+          database.logger.debug("Updating registers for: \(currRoom.room.name)")
+          currRoom.registers = registers
+        }
+        if currRoom.hasChanges {
+          try await currRoom.save(on: database)
+        }
+      } else {
+        database.logger.debug("CREATING NEW TrunkRoomModel")
+        let newModel = try TrunkRoomModel(
+          trunkID: requireID(),
+          roomID: roomID,
+          registers: registers,
+          type: .init(rawValue: type)!
+        )
+        try await newModel.save(on: database)
+      }
+    }
+
+    let roomsToDelete = rooms.filter {
+      !updateRooms.keys.contains($0.$room.id)
+    }
+
+    for room in roomsToDelete {
+      try await room.delete(on: database)
+    }
+
+    database.logger.debug("DONE WITH UPDATES")
+
+  }
 }
diff --git a/Sources/ManualDCore/DuctSizing.swift b/Sources/ManualDCore/DuctSizing.swift
index e165943..9b7b34f 100644
--- a/Sources/ManualDCore/DuctSizing.swift
+++ b/Sources/ManualDCore/DuctSizing.swift
@@ -126,6 +126,8 @@ public enum DuctSizing {
 
 extension DuctSizing {
 
+  // Represents the database model that the duct sizes have been calculated
+  // for.
   public struct TrunkContainer: Codable, Equatable, Identifiable, Sendable {
     public var id: TrunkSize.ID { trunk.id }
 
@@ -141,6 +143,7 @@ extension DuctSizing {
     }
   }
 
+  // Represents the database model.
   public struct TrunkSize: Codable, Equatable, Identifiable, Sendable {
 
     public let id: UUID
@@ -187,6 +190,23 @@ extension DuctSizing.TrunkSize {
     }
   }
 
+  public struct Update: Codable, Equatable, Sendable {
+
+    public let type: TrunkType?
+    public let rooms: [Room.ID: [Int]]?
+    public let height: Int?
+
+    public init(
+      type: DuctSizing.TrunkSize.TrunkType? = nil,
+      rooms: [Room.ID: [Int]]? = nil,
+      height: Int? = nil
+    ) {
+      self.type = type
+      self.rooms = rooms
+      self.height = height
+    }
+  }
+
   // TODO: Make registers non-optional
   public struct RoomProxy: Codable, Equatable, Identifiable, Sendable {
 
diff --git a/Sources/ViewController/Extensions/TrunkSizeForm+extensions.swift b/Sources/ViewController/Extensions/TrunkSizeForm+extensions.swift
index 92b3ef7..2212b38 100644
--- a/Sources/ViewController/Extensions/TrunkSizeForm+extensions.swift
+++ b/Sources/ViewController/Extensions/TrunkSizeForm+extensions.swift
@@ -13,6 +13,14 @@ extension SiteRoute.View.ProjectRoute.DuctSizingRoute.TrunkSizeForm {
     )
   }
 
+  func toUpdate(logger: Logger? = nil) throws -> DuctSizing.TrunkSize.Update {
+    try .init(
+      type: type,
+      rooms: makeRooms(logger: logger),
+      height: height
+    )
+  }
+
   func makeRooms(logger: Logger?) throws -> [Room.ID: [Int]] {
     var retval = [Room.ID: [Int]]()
     for room in rooms {
diff --git a/Sources/ViewController/Live.swift b/Sources/ViewController/Live.swift
index 3461af6..61c4933 100644
--- a/Sources/ViewController/Live.swift
+++ b/Sources/ViewController/Live.swift
@@ -581,8 +581,9 @@ extension SiteRoute.View.ProjectRoute.DuctSizingRoute {
         }
 
       case .update(let id, let form):
-        // FIX:
-        fatalError()
+        return await view(on: request, projectID: projectID) {
+          _ = try await database.trunkSizes.update(id, form.toUpdate())
+        }
       }
     }
   }
diff --git a/Sources/ViewController/Views/DuctSizing/DuctSizingView.swift b/Sources/ViewController/Views/DuctSizing/DuctSizingView.swift
index 89b91ff..7ba38d9 100644
--- a/Sources/ViewController/Views/DuctSizing/DuctSizingView.swift
+++ b/Sources/ViewController/Views/DuctSizing/DuctSizingView.swift
@@ -176,6 +176,7 @@ struct DuctSizingView: HTML, Sendable {
   }
 
   struct TrunkTable: HTML, Sendable {
+
     let trunks: [DuctSizing.TrunkContainer]
     let rooms: [DuctSizing.RoomContainer]
 
@@ -196,86 +197,89 @@ struct DuctSizingView: HTML, Sendable {
           }
           tbody {
             for trunk in trunks {
-              tr {
-                td(.class("space-x-2")) {
-                  // div(.class("flex flex-wrap space-x-2 max-w-1/3")) {
-                  for id in registerIDS(trunk.trunk) {
-                    Badge { id }
-                  }
-                  // }
-                }
-                td {
-                  Number(trunk.ductSize.designCFM.value, digits: 0)
-                }
-                td {
-                  Number(trunk.ductSize.roundSize, digits: 1)
-                }
-                td {
-                  Number(trunk.ductSize.velocity)
-                }
-                td {
-                  Badge(number: trunk.ductSize.finalSize)
-                    .attributes(.class("badge-secondary"))
-                }
-                td {
-                  Badge(number: trunk.ductSize.flexSize)
-                    .attributes(.class("badge-primary"))
-                }
-                td {
-                  if let width = trunk.ductSize.width {
-                    Number(width)
-                  }
-
-                }
-                td {
-
-                  div(.class("flex justify-between items-center space-x-4")) {
-                    div {
-                      if let height = trunk.ductSize.height {
-                        Number(height)
-                      }
-                    }
-
-                    div {
-                      div(.class("join")) {
-                        TrashButton()
-                          .attributes(.class("join-item btn-ghost"))
-                          .attributes(
-                            // .hx.delete(
-                            //   route: .project(
-                            //     .detail(
-                            //       projectID,
-                            //       .ductSizing(
-                            //         .deleteRectangularSize(
-                            //           room.roomID,
-                            //           room.rectangularSize?.id ?? .init())
-                            //       )
-                            //     )
-                            //   )
-                            // ),
-                            .hx.target("closest tr"),
-                            .hx.swap(.outerHTML)
-                            // when: room.rectangularSize != nil
-                          )
-
-                        EditButton()
-                          .attributes(
-                            .class("join-item btn-ghost"),
-                            // .showModal(id: RectangularSizeForm.id(room))
-                          )
-                      }
-                    }
-                  }
-                  // FIX: Add Trunk form.
-                }
-              }
+              TrunkRow(trunk: trunk, rooms: rooms)
             }
           }
         }
       }
     }
 
-    func registerIDS(_ trunk: DuctSizing.TrunkSize) -> [String] {
+  }
+
+  struct TrunkRow: HTML, Sendable {
+
+    @Environment(ProjectViewValue.$projectID) var projectID
+
+    let trunk: DuctSizing.TrunkContainer
+    let rooms: [DuctSizing.RoomContainer]
+
+    var body: some HTML<HTMLTag.tr> {
+      tr {
+        td(.class("space-x-2")) {
+          for id in registerIDS(trunk.trunk) {
+            Badge { id }
+          }
+        }
+        td {
+          Number(trunk.ductSize.designCFM.value, digits: 0)
+        }
+        td {
+          Number(trunk.ductSize.roundSize, digits: 1)
+        }
+        td {
+          Number(trunk.ductSize.velocity)
+        }
+        td {
+          Badge(number: trunk.ductSize.finalSize)
+            .attributes(.class("badge-secondary"))
+        }
+        td {
+          Badge(number: trunk.ductSize.flexSize)
+            .attributes(.class("badge-primary"))
+        }
+        td {
+          if let width = trunk.ductSize.width {
+            Number(width)
+          }
+
+        }
+        td {
+
+          div(.class("flex justify-between items-center space-x-4")) {
+            div {
+              if let height = trunk.ductSize.height {
+                Number(height)
+              }
+            }
+
+            div {
+              div(.class("join")) {
+                TrashButton()
+                  .attributes(.class("join-item btn-ghost"))
+                  .attributes(
+                    .hx.delete(route: deleteRoute),
+                    .hx.target("closest tr"),
+                    .hx.swap(.outerHTML)
+                  )
+
+                EditButton()
+                  .attributes(
+                    .class("join-item btn-ghost"),
+                    .showModal(id: TrunkSizeForm.id(trunk))
+                  )
+              }
+            }
+          }
+          TrunkSizeForm(trunk: trunk, rooms: rooms, dismiss: true)
+        }
+      }
+    }
+
+    private var deleteRoute: SiteRoute.View {
+      .project(.detail(projectID, .ductSizing(.trunk(.delete(trunk.id)))))
+    }
+
+    private func registerIDS(_ trunk: DuctSizing.TrunkSize) -> [String] {
       trunk.rooms.reduce(into: []) { array, room in
         array = room.registers.reduce(into: array) { array, register in
           if let room =
diff --git a/Sources/ViewController/Views/DuctSizing/TrunkSizeForm.swift b/Sources/ViewController/Views/DuctSizing/TrunkSizeForm.swift
index c1aafd7..ea48368 100644
--- a/Sources/ViewController/Views/DuctSizing/TrunkSizeForm.swift
+++ b/Sources/ViewController/Views/DuctSizing/TrunkSizeForm.swift
@@ -5,27 +5,47 @@ import Styleguide
 
 struct TrunkSizeForm: HTML, Sendable {
 
-  static func id() -> String {
-    "trunkSizeForm"
+  static func id(_ trunk: DuctSizing.TrunkContainer? = nil) -> String {
+    let base = "trunkSizeForm"
+    guard let trunk else { return base }
+    return "\(base)_\(trunk.id.idString)"
   }
 
   @Environment(ProjectViewValue.$projectID) var projectID
 
+  let container: DuctSizing.TrunkContainer?
   let rooms: [DuctSizing.RoomContainer]
   let dismiss: Bool
 
+  var trunk: DuctSizing.TrunkSize? {
+    container?.trunk
+  }
+
+  init(
+    trunk: DuctSizing.TrunkContainer? = nil,
+    rooms: [DuctSizing.RoomContainer],
+    dismiss: Bool = true
+  ) {
+    self.container = trunk
+    self.rooms = rooms
+    self.dismiss = dismiss
+  }
+
   var route: String {
     SiteRoute.View.router
       .path(for: .project(.detail(projectID, .ductSizing(.index))))
       .appendingPath(SiteRoute.View.ProjectRoute.DuctSizingRoute.TrunkRoute.rootPath)
+      .appendingPath(trunk?.id)
   }
 
   var body: some HTML {
-    ModalForm(id: Self.id(), dismiss: dismiss) {
+    ModalForm(id: Self.id(container), dismiss: dismiss) {
       h1(.class("text-lg font-bold mb-4")) { "Trunk Size" }
       form(
         .class("space-y-4"),
-        .hx.post(route),
+        trunk == nil
+          ? .hx.post(route)
+          : .hx.patch(route),
         .hx.target("body"),
         .hx.swap(.outerHTML)
       ) {
@@ -38,6 +58,7 @@ struct TrunkSizeForm: HTML, Sendable {
             select(.name("type")) {
               for type in DuctSizing.TrunkSize.TrunkType.allCases {
                 option(.value(type.rawValue)) { type.rawValue.capitalized }
+                  .attributes(.selected, when: trunk?.type == type)
               }
             }
           }
@@ -46,6 +67,7 @@ struct TrunkSizeForm: HTML, Sendable {
             "Height",
             .type(.text),
             .name("height"),
+            .value(trunk?.height),
             .placeholder("8 (Optional)"),
           )
         }
@@ -63,6 +85,10 @@ struct TrunkSizeForm: HTML, Sendable {
                   .name("rooms"),
                   .value("\(room.roomID)_\(room.roomRegister)")
                 )
+                .attributes(
+                  .checked,
+                  when: trunk == nil ? false : trunk!.rooms.hasRoom(room)
+                )
               }
             }
           }
@@ -75,3 +101,12 @@ struct TrunkSizeForm: HTML, Sendable {
   }
 
 }
+
+extension Array where Element == DuctSizing.TrunkSize.RoomProxy {
+  func hasRoom(_ room: DuctSizing.RoomContainer) -> Bool {
+    first {
+      $0.id == room.roomID
+        && $0.registers.contains(room.roomRegister)
+    } != nil
+  }
+}