Calling all artists - mounting picture with "plastic" type cover??

[YLSF]

When I was at the Toronto Outdoor Art Exibit a month or two ago I saw a lot of artists had mounted peices of work with a sheet of heavy acrylic or plastic over the work (either photography, or other work).....

Now, I don't know what this mounting method is called or even how to describe it... I was doing some googling around to find an example but I can't even find anything. Does anyone know what I am talking about?? Better yet, does anyone know where I can get this done or how to do it myself? I have some recent pictures and I would like to blow them up and do this mounting process for them.

[YLSF]

I called Michael's but they don't do what I am looking for...

I could buy the Plexiglass but I don't know how it is applied, the process of actually mounting the picture onto a backing (plywood/foam board/whatever) and then how to mount the plexiglass on top of the picture....

I am hoping someone knows what I am talking about because I don't even know how to google search a solution .. I have tried different options but I am not coming up with what I am looking for.

EDIT: to respond to the post below, I am looking for something that is a "seemless" plexiglass on top.. like, they must have used some kind of glue or something to attach it... I don't want any clips or anything or those "Cheap" wal-mart style frameless frames.... but, thanks for responding anyway!

[CSK'sMom]

I don't know if we are talking about the same thing but.... I have several "frameless" frames. Essentially they are pressboard backerboard and a piece of plexi. It has special clips that attach the two together. IIRC, I picked them up at Walmart or maybe Zellers.