Most Coaster type conversions use long screen doors tipped on their sides to give window security and of course insect protection. This system works well but it does feel like a bit of a prison from inside. Rex and Marlene solved the problem a slightly different way and is looks quite pleasing to the eye. This is because of the light gauge aluminium curved corner inserts simply pop riveted to the frame. Note the special screws used. Hopefully any intending burglar wont have one of these wrenches.