We have one of those cat doors that sets up in the tracks of a sliding glass door. We got one because we set the litter box out on the patio and to let our two girls freedom to come in and out. They were nervous at first with the flap but we taped the magnet down to make it a bit easier for them at first since it was new and the magnet was a bit strong in keeping the flap closed. Now they fly through the house and through the flap no problem.
If it wasn't for the fact that we're on the second floor we might not have ordered one. Not as secure as just having the door lock into its frame as normal.
