They place the Transformer they are used on into a form of stasis lock, which leaves the victim fully conscious and capable of speech, but - once active - unable to move in any other way or use any special powers they may possess.
When Optimus Prime refused to agree to cover up recent events with Megatron and the AllSpark, Sentinel Prime arrested him, and threatened to use a pair of stasis cuffs on him. When he later tried to use them on Optimus, however, he quickly found them on his own wrists. Optimus would get the chance to use the same pair on Starscream later the same day.
When the Cybertron Elite Guard departed Earth, they left a box of stasis cuffs for Optimus' crew to use on any Decepticons they would encounter.
These cuffs were soon put to good use when it was shown that the brig of the Elite Guard's ship could not hold the rogue Decepticon. Prowl, eager to prove himself, took a pair to the moon once he tracked the signature of Starscream's AllSpark fragment there. During the scuffle between Prowl and the bounty hunter Lockdown, Starscream escaped. It is unknown if the cuffs were ineffective against Starscream's unique mechanical makeup, or if one of his clones freed him. Given his ability to break out of the Elite Guard's brig, either is quite possible - but after recovering from Prowl's EMP, Starscream seemed to have his movement limited only by the physical device, as with a human in handcuffs, rather than the statue-like state Sentinel Prime was left in.
A pair Lockdown supplied seemed to be effective enough to restrain another clone, but it was later revealed that this was Starscream's intent. Their true usefulness against Starscream or his clones is presently quite uncertain.