PAL

Ptolemaeus Arabus et Latinus

_ (the underscore) is the placeholder for exactly one character.
% (the percent sign) is the placeholder for no, one or more than one character.
%% (two percent signs) is the placeholder for no, one or more than one character, but not for blank space (so that a search ends at word boundaries).

At the beginning and at the end, these placeholders are superfluous.

having a rectangular cross section ‘having a rectangular cross section’

English

References: Alm. Toomer: 61
Translation of:
Greek: τετράγωνος τὴν ἐπιφάνειαν [Alm. Heiberg: I.12, 64:13]