To slide the saddle fore or aft you probably would loosen both bolts. To adjust tilt however, you will probably need to loosen one, then tighten the other to compensate. So, to lift the nose up some (for example) you would loosen the rear bolt, then tighten the front. The rear bolt should then "feel" tight.
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1989 Schwinn Paramount OS
1980 Mclean/Silk Hope Sport Touring
1983 Bianchi pista
1976 Fuji Feather track
1979 raleigh track
"I've consulted my sources and I'm pretty sure your derailleur does not exist"