Support electrical box?

[toplessHO]

Not always true, if the wrong depth ring is used like a 1/2" raised ring for 1/2" drywall, and/ or sloppy box cut outs in whatever the wall is to be covered in the receptacle will not secure. As to the ring depth, use one that is 1/8 inch deeper then the wall material, for example 5/8" ring for 1/2" material and 3/4" for 5/8" material.

things fit alot better when a good dry waller would cut by hand not with a router.
mot PR rings are made with a taper and when using a router it will make the hole odd shaped and devices ill fitting.
Finishers try and "fix" this with gobs of mud around the boxes most ot the time covering so much of the opening its hard to tell where the box starts and stops.
Yes best to support the heck out of it and not rely on those device ears

 

[alfredeneuman]

The reason for the added 1/8" necessary is this:
Plaster and switch ring's measurements don't take into account the additional thickness of the heads of the 8-32 screws that are used to attach the rings to the boxes, which happens to be 1/8"