Step 4: Drill And Cut An Opening
Use a drill to place a hole at each corner. Next use a large kitchen knife in one of the holes to drive down and cut the tin. Use the knife in this way twice to carve out a wedge to allow shears in to finish the job. Use tin snips or heavy scissors to finish the job.
A note of caution!!! Cut tin is razor sharp, use care and protective gloves as needed to prevent a nasty cut!!