They were used on Spiders with lapbelts. Those hooks went under the rearmost screw of the chrome strip that goes over the door weatherstrip. It is a hook that you can hook the seatbelt's end onto, so it does not fall behind the seat.
Csaba
'71 124 Spider, much modified
'17 124 Abarth, silver http://italiancarclub.com/csaba/
Co-owner of the best dang Fiat parts place in town
Leave it up to Csaba! Thanks guys...excellent, I will give them a try...I hate digging around for those lap belts... Thanks Csaba and Matt. I knew someone would know.