Adjustable square router templates?
I was wondering if there are any adjustable square type of jigs for the router? Whenever I have a project where I have to make a cavity/mortise for something in wood, I end up gluing pieces of wood around the object or cavity measurement lines (double sided tape ends up budging and ruining the projects) and using a flush trim or mortising bit to do the job, then pry off the template pieces with a chisel.
I've had this come up with making a wooden iPhone case and now I'm working on an iPod control foot pedal for my wife's work. She does puppet shows and wanted to make playlists on her iPod she could control sound effects with using her foot since she's got puppets on her hands.
Is there an easier way of doing this?