There is probably a fairly obvious answer to this question, but being a PSP convert I can't seem to find it. What I am looking to do is delete the rectangle at the specific angle shown with the line. I assumed it was draw line, direct selection, click, delete: I was wrong, apparently I've missed some critical step here. Any direction would be most appreciated.
These are vector shape layers. So, they can be edited with the vector tools.
Select the rectangle shape layer in the layers panel
Select the Path Selection tool (A)
Click on the rectangle shape in the image window, to select the path.
Choose the Add Anchor Point tool. Add an anchor
Choose the Convert Point tool
Click on the new Anchor Point you made, to turn it into a corner point.
Choose the Delete Anchor Point tool
Click on the corner anchor of the rectangle to remove it