it's easy to create a wave like that --

create a new layer with a rectangle shape -- it needs to be vertical on the page (you can change it later)

now go to filter->distort->shear
when you see the little thumbnail with the vertical line in it, you can click on the line to add wave points - drag them left or right to create the wave shape you want.

turn your template 90 degrees and you can use it

__________________
Christine Smith