Rotating a rectangle about a point....

I want to rotate a rectangle about a point, but I want the bass to stay put while the rest of the block moves…

The bass?

If you make a rotation around a point the only point that stand still is the pivot.

You can compute the rotation with a rotation matrix.

No, I think he meant the bass.

Anyway, a combination of glRotate/glTranslate should do the trick if you are lost in matrices.