hockeyflow33
Super Freak
Double sided tape? Plates & panel and screw them together (with short screws) from behind? Secure each to the wall behind but not to each other?
My only Best, a height extension unit, has optional feet on the bottom. Where the metal screw thread insert are for the feet there's also a small hole inside the cabinet. If either of yours also have this feature, you could put a screw through this hole from the top one into the bottom one. That would only leave a mark on the top surface of the bottom unit, something easily hidden in the future.
Thanks!
Yea, my thought was to go with brackets on the back or like you said, go through the foot hole and secure it with a bolt.