I thought my house was all 1/2 sheetrock. I was doing some remodeling and removed some ceiling fixtures and replaced with recessed cans. I need to patch the old ceiling boxes. I squared out the holes and attempted to patch with 1/2 sheetrock, but it seems the 1/2 sheetrock "sticks out." I patched holes in the walls, and the 1/2 worked fine. Was there a dimension less than 1/2. It is not 3/8" sheetrock either. I cut back the sheetrock to the joist and then put in a wood nailer (was going to nail to the joist and nailer to put in the patch).