modeling-app/docs/kcl/startSketchOn.md

---
title: "startSketchOn"
excerpt: "Start a sketch on a specific plane or face."
layout: manual
---

Start a sketch on a specific plane or face.



```js
startSketchOn(data: SketchData, tag?: SketchOnFaceTag) -> SketchSurface
```

### Examples

```js
startSketchOn('XY')
  |> startProfileAt([0, 0], %)
  |> line([10, 10], %)
  |> line([20, 10], %, "edge1")
  |> close(%, "edge2")
```

```js
fn cube = (pos, scale) => {
  const sg = startSketchOn('XY')
  |> startProfileAt(pos, %)
  |> line([0, scale], %)
  |> line([scale, 0], %)
  |> line([0, -scale], %)
  |> close(%)
  |> extrude(scale, %)

  return sg
}

const box = cube([0, 0], 20)

const part001 = startSketchOn(box, "start")
  |> startProfileAt([0, 0], %)
  |> line([10, 10], %)
  |> line([20, 10], %, "edge1")
  |> close(%)
  |> extrude(20, %)
```

### Arguments

* `data`: `SketchData` - Data for start sketch on. You can start a sketch on a plane or an extrude group. (REQUIRED)
```js
"XY" |
"-XY" |
"XZ" |
"-XZ" |
"YZ" |
"-YZ" |
{
	plane: {
	// Origin of the plane.
	origin: {
	x: number,
	y: number,
	z: number,
},
	// What should the plane’s X axis be?
	x_axis: {
	x: number,
	y: number,
	z: number,
},
	// What should the plane’s Y axis be?
	y_axis: {
	x: number,
	y: number,
	z: number,
},
	// The z-axis (normal).
	z_axis: {
	x: number,
	y: number,
	z: number,
},
},
} |
{
	// The id of the extrusion end cap
	endCapId: uuid,
	// The height of the extrude group.
	height: number,
	// The id of the extrude group.
	id: uuid,
	// The position of the extrude group.
	position: [number, number, number],
	// The rotation of the extrude group.
	rotation: [number, number, number, number],
	// The sketch group paths.
	sketchGroupValues: [{
	// The from point.
	from: [number, number],
	// The name of the path.
	name: string,
	// The to point.
	to: [number, number],
	type: "ToPoint",
} |
{
	// arc's direction
	ccw: string,
	// the arc's center
	center: [number, number],
	// The from point.
	from: [number, number],
	// The name of the path.
	name: string,
	// The to point.
	to: [number, number],
	type: "TangentialArcTo",
} |
{
	// The from point.
	from: [number, number],
	// The name of the path.
	name: string,
	// The to point.
	to: [number, number],
	type: "TangentialArc",
} |
{
	// The from point.
	from: [number, number],
	// The name of the path.
	name: string,
	// The to point.
	to: [number, number],
	type: "Horizontal",
	// The x coordinate.
	x: number,
} |
{
	// The from point.
	from: [number, number],
	// The name of the path.
	name: string,
	// The to point.
	to: [number, number],
	type: "AngledLineTo",
	// The x coordinate.
	x: number,
	// The y coordinate.
	y: number,
} |
{
	// The from point.
	from: [number, number],
	// The name of the path.
	name: string,
	// The to point.
	to: [number, number],
	type: "Base",
}],
	// The id of the extrusion start cap
	startCapId: uuid,
	// The extrude surfaces.
	value: [{
	// The face id for the extrude plane.
	faceId: uuid,
	// The id of the geometry.
	id: uuid,
	// The name.
	name: string,
	// The position.
	position: [number, number, number],
	// The rotation.
	rotation: [number, number, number, number],
	// The source range.
	sourceRange: [number, number],
	type: "extrudePlane",
} |
{
	// The face id for the extrude plane.
	faceId: uuid,
	// The id of the geometry.
	id: uuid,
	// The name.
	name: string,
	// The position.
	position: [number, number, number],
	// The rotation.
	rotation: [number, number, number, number],
	// The source range.
	sourceRange: [number, number],
	type: "extrudeArc",
}],
	// The x-axis of the extrude group base plane in the 3D space
	xAxis: {
	x: number,
	y: number,
	z: number,
},
	// The y-axis of the extrude group base plane in the 3D space
	yAxis: {
	x: number,
	y: number,
	z: number,
},
	// The z-axis of the extrude group base plane in the 3D space
	zAxis: {
	x: number,
	y: number,
	z: number,
},
}
```
* `tag`: `SketchOnFaceTag` - A tag for sketch on face. (OPTIONAL)
```js
"start" | "end" |
string
```

### Returns

`SketchSurface` - A sketch group type.
```js
{
	// The id of the plane.
	id: uuid,
	// Origin of the plane.
	origin: {
	x: number,
	y: number,
	z: number,
},
	type: "plane",
	// Type for a plane.
	value: "XY" | "XZ" | "YZ" | "Custom",
	// What should the plane’s X axis be?
	xAxis: {
	x: number,
	y: number,
	z: number,
},
	// What should the plane’s Y axis be?
	yAxis: {
	x: number,
	y: number,
	z: number,
},
	// The z-axis (normal).
	zAxis: {
	x: number,
	y: number,
	z: number,
},
} |
{
	// The id of the face.
	id: uuid,
	// The original sketch group id of the object we are sketching on.
	sketchGroupId: uuid,
	type: "face",
	// The tag of the face.
	value: string,
	// What should the face’s X axis be?
	xAxis: {
	x: number,
	y: number,
	z: number,
},
	// What should the face’s Y axis be?
	yAxis: {
	x: number,
	y: number,
	z: number,
},
	// The z-axis (normal).
	zAxis: {
	x: number,
	y: number,
	z: number,
},
}
```