Mascle

In heraldry a mascle is a charge in the shape of a voided lozenge.

Masculy looks similar to fretty, but while the latter is an interlaced fretwork pattern counting as a single charge, the former is a pattern of abutting mascles without interlacing, and is considered semy of mascles. In period this very rare pattern was shown several different ways, including versions which did not touch all the edges of the shield.