Border Pass

This may never be useful to anyone else, but here's a little After Effects trick for making a border around a frame.

Click the shape tool.  Set the stroke to 2 pixels for a one pixel border -if you only do one pixel it's soft and grey.

Make the shape white.

Then click the layers window.  This will make a shape the size of the document.

Set the "mode" to multiply.

This gives you an exact, perfect border.