many metal grey river nuts for hard internal thread for thin units on the upper left part of oblong horizontal, top view on

air airtight background black bolted bow box carving chiselling closure collar connection copy detail embossment enclosure engineering fastener grange grey guard hard hardness high horizontal imagery inner inside internal left metal nut oblong pack ring riv rivet rivnut rustic screw scrimshaw space span surface technical texture thread top toreutics view wing