A sign casing having a structural frame defining a front plane and a planar opening in that front plane. The structural frame has a cleft extending around the front plane. The cleft has a depth dimension extending in a direction substantially parallel to the front plane, and a latching member mounted therein. The sign casing also includes an edging bordering the planar opening. The edging has a flat strip for covering an edge of the planar opening and a latch blade extending perpendicularly from the flat strip. The latch blade has a longitudinal bulge thereon which is engagedly mountable in the latching member of the cleft such that the edging is mountable to the structural frame by simply pushing the blade into the cleft.