Stubborn cat.

This weekend I put a new door in between our basement and first floor. This was something we did with the hope of lowering our heating bills. When I was cutting the door it dawned on me that we forgot to consider how the cats would get downstairs. This was easily solved by cutting a space and adding a pet door. Now that the door is in I am very pleased with the results. The only problem is that one cat refuses to use the door. The other cat immediately went through the door without a problem. How I am going to get the stubborn cat through the door I haven't yet decided.