Adam Clarke on Judges 3:16

A dagger which had two edges, of a cubit length - The word גמד gomed, which we translate cubit, is of very doubtful signification. As the root seems to signify contracted, it probably means an instrument made for the purpose shorter than usual, and something like the Italian stiletto. The Septuagint translate it by σπιθαμη, a span, and most of the versions understand it in the same sense.

Upon his right thigh - Because he was left-handed. Ordinarily the sword is on the left side, that it may be readily drawn out by the right hand; but as Ehud was left-handed, to be convenient his sword must be on the right side.