1) Croisette 2) Crosette 3) Dog-ear 4) Elbow 
• (n.) The shoulder of a joggled keystone. • (n.) A return in one of the corners of the architrave of a door or window; -- called also ancon, ear, elbow.
Cros·sette' noun [ French, dim. of crosse . See Crosier .] (Architecture) (a) A return in one of the corners of the architrave of a door or window; -- called also ancon , ear , elbow . (b) The shoulder of a joggled keystone. 
In architecture, a crosette is a return in one of the corners of the architrave of a door or window.
(Croissette, Crosset) A side lug at the upper side of an arch stone, entering a corresponding space on the adjoining stone.
a projection at a corner of a door or window architrave.