I would like to draw a polygon as follows. I know how to use pen tool or shape builder tool (1 rectangle + 1 triangle - 1 triangle) to do this.

But when I modify the width of shape by moving the anchor, the angle of the triangle change as well. I don't want it to happen; I'm looking for a way to change the width of the shape easily without impacting anything else.

Could anyone help?

[![enter image description here](https://i.stack.imgur.com/mMBXE.png)](https://i.stack.imgur.com/mMBXE.png)