Stick Cylinder is the hydraulic muscle that moves the arm of our excavator forward and backward. It is a big tube with a piston inside. When we send oil in one side, it pushes the piston out and the arm extends. Oil on the other side pulls it back. We keep it clean, check seals for leaks and grease the pivot ends. It is like the hinge on your door, but way stronger. If it leaks, the arm gets slow and floppy.