big one holds the dash wire harness under the steering column, installs at left lower stud of the brake booster bracket, held on with a push on star cut center thin washer like they use on brake drums.
has to be removed from the stud when doing vac brake conversion but doesn't need to be removed from harness
the other two are for the emission canister on the driver fender well, they clip into the bottom of the canister and allow it to bolt to the plastic fenderwell with 10mm bolts