Resize a component easily?

First timer here. Using SketchUp 2017 Make on a Windows 10 laptop. Asking if there is any EASY way to resize a component. I’m making a 3 shelf cart to store my wife’s growing collection of kitchen appliances to free up counter space.

I have long side rails measuring 36" long, ends mitered at 45*, with a 3/4" high rabbet 3/8" deep on the bottoms of each. I would like to copy these rails, with these exact parameters, but somehow make them only 18" long, so basically just take 18" out of the middle

You can select the end and move it with the move tool.
GIF 19-07-2025 12-46-54 PM