Beginner Question

[zp3]

Below the seat on my 65 there are two hyd valves. Below each control knob there is a sliding piece that appears to lock the valve in the open position. What would be a common use of these valves and the locking feature?

 

[Dieseltech]

The left lever is locked back for three point use, and left in the center when using the right lever for external cylinder use. The 65 dad had on the farm years ago, the right lever lock was never used.