Brakes freezing up!
 

I have a 1981 F150 that is in decent shape but I don't drive it very often; maybe a short trip once or twice a month. Lately, each time it sits for a couple of weeks or more, the brakes stick. It will back up ok but doesn't want to move forward. I am able to gradually work them loose by backing up and pulling forward. Why do they stick like this and is there anything I can do, other than just drive it more often, to prevent this? Thanks for any info you have on this subject.

Don't set the parking brake.

There are many possibilities. Any vehicle that sits for a long time can have sticky brakes from rust on the rotors, but yours sounds more like master cylinder/calipers/wheel cylinders or the parking brake sticking. You can start by lubricating all of the components of the parking brake assembly to ensure smooth operation, on and off. At that age, the moisture from condensation in the brake fluid causes rust. Anything with a piston it it can stick after sitting a long time. It may need a flush of the brake fluid, but also rebuilding of the master/wheel cylinders/calipers. It's 36 years old, and those may all be original if only shoes/pads have been changed over the years. Brake internals are subject to corrosion over time regardless of the miles on them.

duplicate, somehow

It sounds like the rears drums are sticking. The truck moving a couple time a month isnt long enough for pads to stick, unless you live in a rain forest. Very well could be the cable, I had to replace the cables on my '85 on an annual basis.