Velcro is a great idea! Thanks! Magnets could also work. I am glad I posted these pics cause I haven't thought of any of those ideas! The side door will be my guinea pig door, I will see what is going to work with that door and repeat it on the front. I put that door in the side to have access to the sump if it needed to come out. I did a lot of planning before and during this build, but funny enough I will probably still miss something that would have been a good idea.