Flag
Flag turns up in 2 fields: electrotechnology, lighting. Here is what it means to the people in each one.
Flag in electrotechnology
Indicator on a protection relay showing which element or phase operated; also the verb for it showing.
A flag, also called a target, is the mechanical or LED indicator on a protection relay that stays set after an operation to show which element tripped, such as A-phase instantaneous or earth fault. Operators record every flag before resetting, because flags are the first evidence of fault type and location. As a verb, a relay that flagged has shown an operation.
"Write down every flag on the panel before you reset anything, I want to know whether the 50 or the 51 flagged."
Flag in lighting
A black fabric panel on a frame used on film sets to block light from hitting part of a scene or the lens.
An opaque black cloth stretched on a wire frame, mounted on a stand with an arm, and placed between a light and the subject to cut spill, shape shadows or keep flare off the lens. Flags come in standard sizes, with long narrow ones called cutters; open-weave nets and translucent silks on the same frames reduce or soften the light rather than block it. To flag a light is to shade part of it this way.
"Flag the top of that 1K off the back wall, the hot edge is drawing the eye away from her face."