Andrew,

It’s a good example of The Porch in action!  Identifications of “whatsits” are
among my favorite topics here.

Since I’d not encountered these before in over 40 years of “tooling around,” I
surmise that this tool must have gone out of style, replaced perhaps by
something less intrusive to the mortar.

John Ruth
Spending some time organizing the shop area today.

Sent from my iPhone