I know someone on my Flist has been looking for this word

[muckefuck]

fent [ad. Fr. fente, f. fendre:--L. findĕre to split.] 1. A short slit or opening in a robe, esp. the opening at the throat, usually closed by a brooch, trimmed with fur, etc. Also a placket or placket-hole. Now chiefly dial.

Comments

[richardthinks.livejournal.com]

The notes to my copy of Shakespeare's Winter's Tale told me that a "placket or placket-hole" was something else entirely.

I guess this is the source of "sword vent" and "riding vents," which I still sometimes come across in jackets and coats.

[muckefuck.livejournal.com]

Well observed! I never would have made that connexion, but the OED itself confirms it.