Exterior This project was spur of the moment and ended up taking me a good two hours due to all the cutting and fitting involved. I spent about $4 on three sheets of gutterguard (better to have extra). Also if you're going to do this have a cutting tool. Unfortunately scissors won't do the job for this. Anywho, I traced the shape out on some cardboard and cut the piece down to fit inside the holes. The top one seemed to fit in perfectly but the bottom two I had to nail into the styrofoam and bend with a dentist tool (fit in pretty well).