I think that in an English wood work setting it’s called a ‘Mullet’.
A piece of wood designed to check the fit of another, that is, not the naff 1970s haircut.
For example, it can be a mortise of a certain size cut in some scrap to check the rough dimension of a series of tenons as you cut them, or conversely a piece of scrap dimensioned as a tenon to check the size and aspect of a particular mortise. Along with many other words, the wood-working term comes, I think, from the French…. which in turn was probably purloined elsewhere.
In the days of hand-made piece-work joinery where the joiner was paid by the dozen or gross, items that had a large number of joints of the same size (for example an order for a couple of hundred doors or chests all the same size) the M&T joints would all be cut and sized alike and checked on a Mullet. For example, 200 doors would have upward of 600- to 800 M&Ts in total – they would never all be individually sized and fitted.
I have a boxfull of old Mullets of all shapes and sizes behind the bench that I’ve had for years. They usually transition into firewood after a decade or two………….