Commentaire sur L’Exode 31:5

ובחרשת denotes artisanship generally, as (Isaiah 40:20) “a clever artisan (חרש חכם)”. Onkelos, however, more closely defines the term each time it occurs in this verse and varies the definition he gives of them: the first he renders by אמנות and the second by נגרות, because the lapidary is called in Aramaic אמן, whilst the worker in wood is called נגר, and he therefore uses the abstract forms of these nouns to specify the particular kind of artisanship here intended.

למלאת TO SET IN — i. e. to put it into its setting, so as to fill it in (למלאת) by making the setting according to the size of the bottom of the stones and its thickness.