securicula
From LSJ
sĕcūrĭcŭla: ae, f.
dim. securis.
I A little axe, a hatchet, Plaut. Rud. 4, 4, 114 sq.; Mart. 14, 35 in lemm. (but Plin. 18, 19, 49, § 177, sericulam).—
II Transf., in carpentry, a mortise in the shape of a hatchethead, a dovetail, Vitr. 4, 7, 4; 10, 17 (10, 11, 8).