How can I easily create a shape with a specific pixel width and height in Photoshop?

So this may sound like an easy question, but it is not.

In webdesign we often use rectangular or square shapes to represent backgrounds for sidebars etc. These need to be pixel perfect so that when it goes into HTML cut up the correct dimensions are preserved.

When drawing a rectangular shape it will often snap/move one or two pixels when the mouse is let go. I can see in the inspector pane that the dimensions are correct when I let go of the mouse, but I then witness Photoshop redistribute the dimensions as it sees fit.

Is there a way I can just enter a pixel height and width as numbers for shapes like with the rectangular marquee tool? Alternatively is there some way to stop this movement occurring?

Answer

This is very easy

For Marquee selection :

For shapes (all kind of) :