Who lays them and when
During the blocking rehearsal and crew show, the 2nd AC watches for each place an actor stops and puts down a mark, often calling "Hold there, marking." Different shows have different habits, but a set might use:
| Mark for | Color | Shape |
|---|---|---|
| Maya (cast #1) | Red | T, top of T toward camera |
| Joe (cast #2) | Blue | T |
| Background start positions | White | Small dash |
| Dolly start and end | Yellow | Line across track or wheel marks |
| Camera tripod legs | Orange | Three spike marks |
The T shape shows where the actor's toes go. On an actor's second position in a scene, the AC might add a small number: "Red 2."
Why camera needs them
The 1st AC pulls focus by distance, not by looking through the lens. During rehearsal they measure from the camera's sensor plane to each mark and write the distances on their follow-focus disc or wireless handset: 8'3" for Maya's first mark, 5'6" for her second. If an actor lands a foot short on a long lens with a shallow depth of field, the take is soft. Marks let the AC trust the numbers.
Lighting depends on marks too. The gaffer may set a small key light that only hits an actor's face correctly within a few inches of the mark.
On set, in practice
"Back to one" means everyone returns to their first marks for another take. Stand-ins stand on the actors' marks while electric lights the scene, so the marks have to survive foot traffic, cable runs, and dolly track being laid around them. On carpet, ACs sometimes use a different tape that won't damage the fiber. Outdoors on grass, they switch to small stakes or sandbags.
Common problems
Marks pulled up by accident. A grip laying dolly track can pick up a mark with a piece of track, and the AC finds out when an actor asks where to stand.
Marks that change without notice. If the director adjusts blocking on take four and nobody tells the camera team, the 1st AC is focusing to a mark the actor is no longer hitting.
Wrap cleanup. Tape left on a location's hardwood floors is a common damage complaint in location returns. The camera team pulls marks at the end of each scene, and the location manager checks before the company leaves.