Dan and other Gentle Galoots,

I hate to disagree with my esteemed colleagues, but according to Salaman's
Dictionary of Woodworking Tools, the following picture shows a donkey's ear,
more precisely "Donkey's Ear Shooting Board", used for "planing a mitre in the
thickness of a board (e.g. along its edge rather than across its end." This is
one I made recently just for the fun of it.

 https://vault.myvzw.com/webcs/C0N4aKRC8C 


Next is a picture of what Salaman calls a "Mitre Shooting Block" or "Mitre
Jack", made by our own Adam Maxwell:

https://maxwells.smugmug.com/Woodworking/Poplar-bookcase/i-rN9XJ6h/A


Salaman says that "In use the workpiece, which has been sawn to a mitre, is
cramped between the triangular blocks, and the joint trued with the Plane."

Translations:   "Mitre" == "Miter" and "cramped" == "clamped". 

Cheers,
Chuck Taylor
north of Seattle USA


===
 Dan asks… 

> Does anyone have any idea what this this is:

It’s a donkey’s ear.