A long time ago , I was a logger..
One day somebody says the tracks need adjusting on the TD 15... Bulldozer.
So I said what do they use to do that ? Guy says grease gun.. I go FO, youre BSing me...
But he says no really.
Soon after that, the boss pulled a cover off the side, hooked up the greasegun..
Started pumping away and lo and behold..the track picked up and slowly tightened up.
Amazing...
I had never thought it through, and realized how much that amount of force on the handle , moving a small piston produces so much psi.!
That is why we use it on stuff like brake calipers and MC,s.