Climber: ON BELAY? = Is the system ready and checked?
Belayer: BELAY ON = Yes, I’m ready to belay you.
Climber: CLIMBING
Belayer: CLIMB ON = You can climb.

Climber: UP ROPE! = Take any extra slack.

Climber: SLACK! = Give me slack.

Climber: TAKE! = Take any extra slack; I’ll sit in the harness.

Climber: WATCH ME! = I’m likely to fall; be ready.

Climber: FALLING! (or aaaah!) = Catch me!

Climber: ROCK! = Take cover; something is falling. Regardless of what is falling (rock, carabiner, etc.), yell “Rock!”

Climber: CLIPPING! = Give me slack; I’m about to clip the rope.

Climber: HALFWAY! = Half of the rope is in use.

Climber: THAT’S ME! = Climber telling the belayer that they pulled all the rope and there is no more slack.

Climber on descent: OFF RAPPEL! = I’m done rappelling; your turn.

Climber: TENSION = Take all the slack in the system. Same as “Take” but usually said at the top of a climb.
Belayer: TENSION ON = There is no slack in the system, you can sit in the harness.
Climber: READY TO LOWER = I’m ready to be lowered.
Belayer: LOWERING = I’m about to lower you.

Climber: OFF BELAY = I’m safe now; you can take me off belay.
Belayer: BELAY OFF = I took you off the belay system.

Climber: ROPE! = Anyone down there? Watch out; I’m about to throw a rope.

Using names: When there are several climbing parties, no visual contact, or a possibility of confusion, use your partner’s name along with your command.