these racks were created with leftover shutter doors from a closet, plastic corner bead for drywall for the racks, and were done for 16x20 canvas (16 1/2" opening). Other ones were made at 30" wide, which will also hold 24" wide. The canvasses lay flat, separated by 2" above and below, and the sheet in front does not touch the edges of the canvas. I have 3 dogs and this system keeps the doggie hair from settling on the paintings.
Hope this helps. These have been added to all the way up to the ceiling now.