Marked position—tape on floor or wall—where actor or object must hit. Essential for timing, light setup, and focus.
Gag Line
On set, you need them daily — without them, it gets chaotic. The gag line (or tape mark) is your silent assistant for precise positioning of actors and objects in space. Usually marked with gaffer tape, adhesive tape, or chalk, it defines exactly where someone must stand, sit, or perform a movement. The name is misleading: it's not about gags in the sense of humor, but about the English idiom "to gag" — to hold something, to fix.
Why is this practically indispensable? Because your lighting, your depth of field, and your camera image vary inch by inch. If you light an actor with hard light from the left and they drift 30 cm to the right, they lose the modeling, their eyes fall into shadow. The focus puller needs a secure position — otherwise, you'll ruin the whole take with blur. Gag lines give you reproducibility across multiple takes. This is especially essential for close-ups or rapid cuts, where continuity errors are immediately visible.
In practice: You determine the exact position together with the focus puller and the First AD. The First Assistant Director (or your script supervisor) notes where the mark is — "Actor A, two steps left of the window, foot on T-mark." In parallel camera setups (multi-cam), multiple marks are set, one for each camera position. For moving shots, you lay gag lines along the route — an important tool during blocking and rehearsal. In exterior light or dynamic scenes, many DoPs use more subtle markings: a taut thread, a floor mark with a tape end, or they work with natural references in the frame (door frame, furniture edge).
The most common beginner mistake: Leaving marks too visible in the frame. Your gag lines must disappear in the finished frame — either outside the frame, under furniture, or so subtly that the camera doesn't capture them. Black duct tape works better on dark surfaces than white. On hardwood floors or light surfaces, professionals work with tape placed low at the edge of the frame or with chalk marks that are later wiped away.