1. A holder for use in interlocking laterally engaging shelf panels comprising: a rectangular member having two bifurcated portions defining rectangular grooves opening outwardly of said member one perpendicular to the other, one bifurcated portion at one end of said member extending beyond the common end of said other of said bifurcated portions for frictionally engaging with the outer surface of a supporting shelf arm, and a stop positioned in said groove of said one of said bifurcated portions for limiting the sliding engagement of said one end thereof over the shelf supporting arm, said grooves extend the full length of said member.

4. A display shelf comprising in combination: a pair of elongated narrow arms for attachment to a vertical wall at substantially the same level, an extension for each of said arms comprising bifurcated channel members for insertion over, resting on the top of, and extending beyond the free ends of each of said arms, each channel member being contoured at its free end for receiving in a sliding fit a panel holder, a pair of panel holders one for each of said channel members, said panel holders being conformed for slidingly fitting onto the end of said arms and each being provided with a pair of grooves substantially perpendicularly to each other, a plurality of panels, the ends of two of said panels being inserted one in a common groove in each of said panel holders and arranged to extend along and rest on the top surface of a different one of said channel members, and a third panel having a different one of its ends inserted in the other of said grooves in each of said panel holders.