Years ago, when I was a copier repairman for 3M Company, I also worked for the Industrial Tape division repairing box sealing equipment - machines that sat at the end of a production line where they folded boxes and taped them shut.
Depending on the model, these machines were either electrical, pneumatic, hydraulic, or some combination of the three. I was only called out to fix these machines when the client's plant maintenance people could not.
I have not worked on hydraulic equipment since, but this week I get my chance.
Our 5th wheel trailer has four slide-outs, and the hydraulic cylinder that drives the biggest one has failed. It has been leaking for some time, and it finally got bad enough to require replacement. I removed the bad cylinder a week or so ago, and ordered a replacement.
Incidentally, I was only able to get the old cylinder off because I had a 1 1/16 inch box end wrench that I inherited from my dad. I have no idea what he used it for, but this is the first time I have ever used it in forty years.
The new cylinder is due to arrive today via UPS.