They are plenty sturdy! And you just tighten the screws on the side till you have fair drag against it moving.
There is a hole already in the mirror where you can insert an allen wrench and turn the mirror to remove from it's windshield base - that's the one you tap .. just twist it in a circular direction (un screw it basically about a 1/4 turn or so). If you have the autodimming, there is enough slack in the wires where it goes back into the homelink wiring to lower it and get it tapped. You'll need to pull the dome light assembly to pull the slack back up after / while putting the mirror in place.