Smith Machine

How to adjust

Rotate the bar about a quarter turn to release it from the rail hooks, choosing the hook notch at shoulder height when standing (or chest height for a lying press).
Set the safety stops/pins on the rails just below your lowest rep position, so they can catch the bar if you run out of strength.
Load weight plates onto both ends of the bar and secure them with plate collars.
For pressing exercises, roll a flat or adjustable bench into position directly under the bar before getting into position.

Get into position for your exercise (stand under the bar to squat, lie on the bench to press...), grip the bar, then rotate it to unlock it from the hooks.
Perform the movement along the bar's fixed vertical path, controlling it on both the lift and the lower.
For squats or lunges, step your feet slightly forward since the bar travels straight down rather than the natural arc of a free bar.
After your last rep, guide the bar back to hook height and rotate it to re-lock onto the hooks before releasing your grip.

Rotate the bar about a quarter turn to lock it securely onto both rail hooks before releasing your grip, and twist it the other way to unlock at the start of a set — this rotating hook is the Smith machine's core safety mechanism.
Always set the safety stops on the rails to the notch just below your lowest rep position before loading weight.
If you fail mid-rep, don't grind it out: hold the bar where it is and rotate your wrists to hook it onto the nearest notch — the hooks run the full length of both rails, so it parks at almost any height; if you can't turn it, lower the bar onto the safety stops, let go, and only then slide out from under it.
Do not lock the knees or elbows out hard at the top of the movement.
Load plates evenly on both ends and secure with collars so the bar doesn't become unbalanced.