A lighting stand, boom, or music stand that cannot maintain its set height and slowly slides downward under a load. This is typically caused by stripped threading, worn friction collars, or over-tightened clutches that no longer grip the inner pipe. Sinkers are a major nuisance on set because they ruin precise focus calls and can be dangerous if a heavy luminaire drops suddenly.
Grab a roll of gaff tape to lock off this stand, the clutch is totally shot and it's a sinker.
Never try to fix a sinker by overtightening the T-handle with a wrench; you will only crush the internal pipe and ruin the stand completely.
Related terms
Focus call
The scheduled crew session in which the lighting designer directs electricians to aim and shape every fixture.
Practical
A working light fixture that appears in the scene itself, such as a table lamp, sconce or neon sign.
Luminaire
The whole light fixture as one product: light source, optics, housing, driver or ballast and power connection.