I have about 12 same-sized plaques I want to hang in my hobby room. The grooves on the back are at different heights, which is making hanging them at the same level difficult.
I'm looking for suggestions please. Since I won't be moving them again I'm even open to using adhesive if it's quick-setting. (I tried using velcro but it tended to slip).

A grooved shelf?

I'd say a small long bracket to support the bottoms of them (essentially a very narrow shelf, as stated above) and something easily removable (like a small "Z" bracket secured with a small screw to the wall?) at the top of each to keep them from tipping off.

Read a tip on this the other day, but haven't tried it yet.
Take some double sided tape and place it just under the groove on the back of each plaque. Stick a thumb tack to the tape where the nail should go. Then just line the plaque up on the wall where you would like it to go and give it a light press. The tack will leave a small hole where the nail should go. As long as you can line the tops of all the plaques up, the holes will take care of themselves.

Hope it helps...

Jamie

The same concept of this tool can be used for pictures with brackets instead of wire...just make it out of flat stock with a sharp point.

Wish I had a better illustration, I can take a picture of the actual tool if need be.

Okay, I decided to go with the 'shelf' (basically a piece of decorative wood trim painted to match the door trim. Mock-up looked good; I'm gonna put it up tonight. Thanks for the advice guys.