Anyway, out by a very old shed that we're fixing up, my husband found this thing while tearing out a recently added slab of cement. It was underneath. It's white ceramic, approximately 3-1/2" long by 3/4" wide. One side has a recessed rectangle with a diamond shape in the middle and the opposite side has three grooved channels. There are two holes for, I assume, screws or nails.
I think it might be some kind of old insulator for knob-and-tube wiring but am not sure. Thanks!
![Image](http://i78.photobucket.com/albums/j105/SimMama/House/found%20ceramic%20piece_zpsvlkynuap.jpg)