Officials give the “wind the clock” clock signal to inform the clock operator to 1) start the clock or 2) keep the clock running. For example, the R will give a “silent wind” after a runner is downed inbounds beyond the line-to-gain and the ball is marked ready for play (an official, typically the umpire, has placed the ball on the ground and has backed away).
When wings should give the “wind the clock” signal:
The runner is downed short of the line-to-gain and close to the sideline
The covering wing will give the wind the clock signal to inform the clock operator to keep the clock running. Sometimes, the runner will be downed inbounds and then roll OOB. Sometimes, the runner’s forward progress will be stopped inbounds, and then the runner will be thrown sideward or backward OOB. The clock operator will see the runner physically OOB and may stop the clock. So, It’s important to give the “wind the clock” (keep the clock running) signal if the ball is dead by rule, inbounds, short of the LTG, and close to the sideline.
In this play, the line judge winds the clock when the runner is downed inbounds close to the sideline. I like this wing’s mechanics for a few additional reasons: he backs out to ensure his safety is not in jeopardy, allowing him to focus on the players and not himself. He also does not rush into the players to mark the forward progress spot. He smoothly advances to the forward progress spot while keeping his eyes on the players.
In this video, the runner’s forward progress is stopped inbounds, and then he is tackled near the sideline. The linesman should give the wind-the-clock signal.
In this clip, the runner’s forward progress is stopped inbounds at the B-45, and the runner is then pushed backward out of bounds at the B-47. The covering official must give the “wind the clock” signal and then move to the forward progress spot. It looks like the linesman marked forward progress at the B-47.
The runner is downed inbounds beyond the LTG
Wings do NOT give the wind the clock signal followed by the kill-the-clock signal. They give only the kill-the-clock signal and then let the R know if the runner was downed “inbounds” (start the clock after the ball is marked RFP) or “OOB” (start the clock on the snap).
On Free Kicks
The wings’ keys are the four K players on their side of the field. In most cases, the R will be the only person who will watch the ball/receiver. If the ball “threatens” the wing’s/umpire’s sideline, only then will he take a quick look at the ball. If the receiving team touches the ball near the wing’s/umpire’s sideline/pylon, then the covering official will give the “wind the clock” signal. If any official other than the R gives the “wind the clock” signal when the ball is between the hashes, it is clear he is ball-watching and is not watching his/her key.
A wing inadvertently kills the clock
(I’ve done this many times.) The wing can give a “wind the clock” signal to inform the clock operator to restart the clock.