Years ago I bought a set of masks for various size papers. Each mask was comprised of two pieces, the outer piece had an outside dimension that matched the paper, e.g. 8 x 10. This was placed on the paper before exposure and covered aprox 1" all around the paper. Then having made the exposure you place the inner mask inside the outer mask, then remove the neg and expose. The outer edge of the inner mask had a 1/8" clear border.
This gave me a print with a 1" white border and a 1/8" black border around the image itself.
I have searched everywhere and can't find this type mask, tried several stores that sell darkroom supplies, nobody knows what I'm talking about. Can't find them at Adorama either.
Can anyone out there help.