Window clip-on type- yes remember those. Also long fibreglass? whips which clipped under a small hook screwed to the roof gutter to stop them waving about too much!
Best replacement type was an old galvanised coathanger jammed into the remains of the vandalised original telescopic- they were never messed about with for some reason
If the car was a banger (or an old van) a UHF socket mounted in the middle of the roof with a bit of welding rod soldered into the centre pin of a UHF plug was pretty robust and was easily removed if required.
An interchangeable selection cut to 1/4 wave for either FM radio or 2m Ham band and with a longer one for AM broadcast graced my old 400E van about 35 years ago.