Is there such thing as an adjustable framing guide?

Question: Is there such thing as an adjustable framing guide!?

Sorry if the question is confusing!.

I'm looking for some kind of framing template!. I mean a fully adjustable neutral 'mount' or 'frame', to help me select an area of a painting and envisage how I want the picture framed!.!.!.

Does anything like this exist!?
Thanks much!Www@QuestionHome@Com

Best Answer - Chosen by Asker:

I usually mount my paintings!.drawings and prints behind card mattes,to protect them!.When I make a mess of a mount I save it as two L-shaped pieces of card,which can be used to test a mount's width and colour before starting on a particular mount!.Just as an extra my friend uses his offcuts to make arty bookmarks,waste no,want not,they do actually sell very well!Www@QuestionHome@Com