It is likely that in an average days metal detecting, you will find many bits of old lead. In times gone by, lead was a valuable source, and was used for making so many different kinds of artefacts. This included Buttons, Weights, Seals to name a few.
One piece of lead that you may find is a potmend. I must admit that until recently I had no idea what one was. So my guess is there are others who may not know either.
From Roman times, when a valued ceramic pot got cracked, rather than chuck it, they mended it. The easiest way to do this was to drill a hole at the end of the crack and then pour molten lead into it whilst placing a flat object at the back to stop the lead all running away.
This formed a plug of lead in the hole with a larger splayed out and flattened area of lead both inside and outside the pot. This both sealed the hole and stopped any further cracking. Most of these are small but all are of a very distinctive shape with two flat areas separated by a thin, circular plug in the centre.
Some of these potmends will come complete with a bit of pottery, still intact. Others will have worked their way free. The potmend method was used all the way through to medieval times.
Here are a couple of examples
My thanks must go to Tom on UKDetectornet, who helped educate me on the above.