diff --git a/packages/viewer-sandbox/src/Extensions/SectionCaps.ts/SectionCaps.ts b/packages/viewer-sandbox/src/Extensions/SectionCaps.ts/SectionCaps.ts
new file mode 100644
index 000000000..3127208fa
--- /dev/null
+++ b/packages/viewer-sandbox/src/Extensions/SectionCaps.ts/SectionCaps.ts
@@ -0,0 +1,95 @@
+import {
+  DefaultPipeline,
+  Extension,
+  IViewer,
+  ObjectLayers,
+  SectionTool,
+  SectionToolEvent
+} from '@speckle/viewer'
+import {
+  FrontSide,
+  KeepStencilOp,
+  Matrix4,
+  Mesh,
+  MeshBasicMaterial,
+  NotEqualStencilFunc,
+  Plane,
+  PlaneGeometry,
+  Quaternion,
+  Vector3
+} from 'three'
+import { SectionCapsPipeline } from './SectionCapsPipeline'
+
+export class SectionCaps extends Extension {
+  protected planeMesh: Mesh
+  protected _enabled = false
+
+  public get enabled(): boolean {
+    return this._enabled
+  }
+  public set enabled(value: boolean) {
+    this._enabled = value
+    if (value) {
+      this.viewer.getRenderer().pipeline = new SectionCapsPipeline(
+        this.viewer.getRenderer()
+      )
+    } else {
+      this.viewer.getRenderer().pipeline = new DefaultPipeline(
+        this.viewer.getRenderer()
+      )
+    }
+  }
+
+  public get inject() {
+    return [SectionTool]
+  }
+
+  constructor(viewer: IViewer, protected sectionTool: SectionTool) {
+    super(viewer)
+
+    this.planeMesh = new Mesh(
+      new PlaneGeometry(1, 1),
+      new MeshBasicMaterial({
+        color: 0x047efb,
+        side: FrontSide,
+        stencilWrite: true,
+        stencilFunc: NotEqualStencilFunc,
+        stencilFail: KeepStencilOp,
+        stencilZFail: KeepStencilOp,
+        stencilZPass: KeepStencilOp
+      })
+    )
+    this.planeMesh.renderOrder = 5
+    this.planeMesh.layers.set(ObjectLayers.OVERLAY)
+    viewer.getRenderer().scene.add(this.planeMesh)
+
+    this.sectionTool.on(SectionToolEvent.Updated, (planes: Plane[]) => {
+      const obb = this.sectionTool.getBox()
+      this.planeMesh.matrixAutoUpdate = false
+      this.planeMesh.matrix.copy(
+        this.getPlaneTransform(
+          // Top facing plane
+          planes[5],
+          new Vector3(2 * obb.halfSize.x, 2 * obb.halfSize.y, 1)
+        )
+      )
+    })
+  }
+
+  protected getPlaneTransform(plane: Plane, scale: Vector3) {
+    const obb = this.sectionTool.getBox()
+    const n = plane.normal.clone().normalize().negate()
+
+    const up = Math.abs(n.z) < 0.999 ? new Vector3(0, 0, 1) : new Vector3(0, 1, 0)
+    const t1 = new Vector3().crossVectors(up, n).normalize()
+    const t2 = new Vector3().crossVectors(n, t1).normalize()
+
+    const basis = new Matrix4().makeBasis(t1, t2, n)
+    const q = new Quaternion().setFromRotationMatrix(basis)
+    const p = plane.projectPoint(obb.center.clone(), new Vector3())
+
+    const worldTRS = new Matrix4().compose(p, q, scale)
+
+    return worldTRS
+  }
+}
diff --git a/packages/viewer-sandbox/src/Extensions/SectionCaps.ts/SectionCapsPipeline.ts b/packages/viewer-sandbox/src/Extensions/SectionCaps.ts/SectionCapsPipeline.ts
new file mode 100644
index 000000000..f181bb627
--- /dev/null
+++ b/packages/viewer-sandbox/src/Extensions/SectionCaps.ts/SectionCapsPipeline.ts
@@ -0,0 +1,27 @@
+import {
+  DefaultPipeline,
+  ObjectLayers,
+  ObjectVisibility,
+  PipelineOptions,
+  SpeckleRenderer
+} from '@speckle/viewer'
+import { StencilFrontPass } from './StencilFrontPass'
+import { StencilBackPass } from './StencilBackPass'
+
+export class SectionCapsPipeline extends DefaultPipeline {
+  constructor(speckleRenderer: SpeckleRenderer, options?: PipelineOptions) {
+    super(speckleRenderer, options)
+
+    const stencilFrontPass = new StencilFrontPass()
+    stencilFrontPass.setLayers([ObjectLayers.STREAM_CONTENT_MESH])
+    stencilFrontPass.setVisibility(ObjectVisibility.OPAQUE)
+
+    const stencilBackPass = new StencilBackPass()
+    stencilBackPass.setLayers([ObjectLayers.STREAM_CONTENT_MESH])
+    stencilBackPass.setVisibility(ObjectVisibility.OPAQUE)
+
+    this.dynamicStage.splice(3, 0, stencilFrontPass, stencilBackPass)
+    this.progressiveStage.splice(4, 0, stencilFrontPass, stencilBackPass)
+    this.passthroughStage.splice(1, 0, stencilFrontPass, stencilBackPass)
+  }
+}
diff --git a/packages/viewer-sandbox/src/Extensions/SectionCaps.ts/StencilBackPass.ts b/packages/viewer-sandbox/src/Extensions/SectionCaps.ts/StencilBackPass.ts
new file mode 100644
index 000000000..67796d60e
--- /dev/null
+++ b/packages/viewer-sandbox/src/Extensions/SectionCaps.ts/StencilBackPass.ts
@@ -0,0 +1,27 @@
+import { GeometryPass, SpeckleBasicMaterial } from '@speckle/viewer'
+import { BackSide, DecrementWrapStencilOp, NoBlending } from 'three'
+
+export class StencilBackPass extends GeometryPass {
+  private stencilBackMaterial: SpeckleBasicMaterial
+
+  get displayName(): string {
+    return 'STENCIL-BACK'
+  }
+
+  get overrideMaterial(): SpeckleBasicMaterial {
+    return this.stencilBackMaterial
+  }
+  constructor() {
+    super()
+
+    this.stencilBackMaterial = new SpeckleBasicMaterial({ color: 0x0000ff }, [])
+    // this.stencilBackMaterial.colorWrite = false
+    this.stencilBackMaterial.depthWrite = false
+    this.stencilBackMaterial.side = BackSide
+    this.stencilBackMaterial.stencilWrite = true
+    this.stencilBackMaterial.stencilFail = DecrementWrapStencilOp
+    this.stencilBackMaterial.stencilZFail = DecrementWrapStencilOp
+    this.stencilBackMaterial.stencilZPass = DecrementWrapStencilOp
+    this.stencilBackMaterial.blending = NoBlending
+  }
+}
diff --git a/packages/viewer-sandbox/src/Extensions/SectionCaps.ts/StencilFrontPass.ts b/packages/viewer-sandbox/src/Extensions/SectionCaps.ts/StencilFrontPass.ts
new file mode 100644
index 000000000..edbed6b09
--- /dev/null
+++ b/packages/viewer-sandbox/src/Extensions/SectionCaps.ts/StencilFrontPass.ts
@@ -0,0 +1,25 @@
+import { GeometryPass, SpeckleBasicMaterial } from '@speckle/viewer'
+import { FrontSide, IncrementWrapStencilOp, NoBlending } from 'three'
+
+export class StencilFrontPass extends GeometryPass {
+  private stencilFrontMaterial: SpeckleBasicMaterial
+
+  get displayName(): string {
+    return 'STENCIL-FRONT'
+  }
+
+  get overrideMaterial(): SpeckleBasicMaterial {
+    return this.stencilFrontMaterial
+  }
+  constructor() {
+    super()
+
+    this.stencilFrontMaterial = new SpeckleBasicMaterial({ color: 0xff0000 }, [])
+    this.stencilFrontMaterial.side = FrontSide
+    this.stencilFrontMaterial.stencilWrite = true
+    this.stencilFrontMaterial.stencilFail = IncrementWrapStencilOp
+    this.stencilFrontMaterial.stencilZFail = IncrementWrapStencilOp
+    this.stencilFrontMaterial.stencilZPass = IncrementWrapStencilOp
+    this.stencilFrontMaterial.blending = NoBlending
+  }
+}
diff --git a/packages/viewer-sandbox/src/Sandbox.ts b/packages/viewer-sandbox/src/Sandbox.ts
index 11aba1a1e..0f7e545b6 100644
--- a/packages/viewer-sandbox/src/Sandbox.ts
+++ b/packages/viewer-sandbox/src/Sandbox.ts
@@ -59,6 +59,7 @@ import {
   ObjectLoader2Flags,
   ObjectLoader2Factory
 } from '@speckle/objectloader2'
+import { SectionCaps } from './Extensions/SectionCaps.ts/SectionCaps'
 
 export default class Sandbox {
   private viewer: Viewer
@@ -433,6 +434,8 @@ export default class Sandbox {
       }
       this.viewer.getExtension(SectionTool).setBox(box)
       this.viewer.getExtension(SectionTool).toggle()
+      const sectionCaps = this.viewer.getExtension(SectionCaps)
+      if (sectionCaps) sectionCaps.enabled = !sectionCaps.enabled
     })
 
     const toggleSectionBoxVisibility = this.tabs.pages[0].addButton({
diff --git a/packages/viewer-sandbox/src/main.ts b/packages/viewer-sandbox/src/main.ts
index e40cfdbda..3f689ba2e 100644
--- a/packages/viewer-sandbox/src/main.ts
+++ b/packages/viewer-sandbox/src/main.ts
@@ -56,6 +56,7 @@ const createViewer = async (containerName: string, _stream: string) => {
   const boxSelect = viewer.createExtension(BoxSelection)
   boxSelect.realtimeSelection = false
   viewer.createExtension(PassReader)
+  // viewer.createExtension(SectionCaps)
 
   const sandbox = new Sandbox(controlsContainer, viewer, multiSelectList)
 
diff --git a/packages/viewer/src/index.ts b/packages/viewer/src/index.ts
index ff980a26c..6d032c6ea 100644
--- a/packages/viewer/src/index.ts
+++ b/packages/viewer/src/index.ts
@@ -114,6 +114,8 @@ import {
   ProgressiveGPass
 } from './modules/pipeline/Passes/GPass.js'
 import {
+  PipelineOptions,
+  BasePipelineOptions,
   DefaultPipelineOptions,
   Pipeline
 } from './modules/pipeline/Pipelines/Pipeline.js'
@@ -283,6 +285,8 @@ export {
   ArcticViewPipeline,
   TAAPipeline,
   ShadedViewPipeline,
+  PipelineOptions,
+  BasePipelineOptions,
   DefaultPipelineOptions,
   DefaultEdgesPipelineOptions,
   ViewModes,