Never seemed fair to nail the "lazy" tag so permanently on the "Susans" but that probably has no "bearing" on the issue. Also called turntable bearings, they are the square or circular flat ball bearing devices YOU bolt between two flat objects to achieve rotation. Like that spinning center section of a Chinese restaurant table. We had these in surplus once and they were quite popular. To our chagrin, we discovered they could be bought commercially for the same price. So we did. The 4" square version is rated for a 300lb. load and the 12" round for 1000lbs.