Does anyone know how to only move the Middle point in photoshop?

for example: You have a square and when you do a transform action on it it makes 8 points (3 on top, 3 on bottom and 1 on each side. Now everytime I use ctl or alt I can only transform the points on the edges. I need to transform only the middle one on the top and bottom, to make somewhat of a triangle shape.

Any suggestions?