gallet

[gal-it] /ˈgæl ɪt/
noun
1.
spall (def 1).
verb (used with object)
2.
to fill (a mortar joint) with gallets.
Also, galet, garret.
Origin
1705-15; < French galet pebble, Old French galet, jalet, derivative of Old North French gal pebble (said to be < Celtic, but MIr gall “pillar stone, standing stone” is only point of comparison)