Directly from the rulebook:
MANDATORY COLLAR / CARRYING OF THE LEAD -
For technical insurance
reasons, the handler must carry a lead throughout the entire course of the
trial. This includes a requirement that the dog must wear a collar at all times.
During off-lead exercises, the lead must be carried out of sight, or hung
around the body in such a way that the catch is on the side of the body
opposite the dog, or in a left to right fashion across the body.
During the trial, the dog must be exhibited with a chain collar in the neutral
position with the lead attached only to the dead ring. Only single-row
medium or wide linked chain collars are permitted. The collar may not have
spikes, sharp points, prongs, or other hooks. The collar must fit loosely
around the dog's neck. Leather, nylon, spike, pinch, or remote training
devices are not permitted in a USCA sanctioned event. "Flea and tick" collars
and tags are to be removed. A chain collar, a leather collar, or a harness is
permitted only for the BH examination.
The composition of the metal collar, especially in regard to weight, should
not deviate from the customary design. If the judge suspects manipulation
by the handler, he / she can demand a change of collars. However, this must
take place before the beginning of the trial phase. If the judge detects intent
to deceive (concealed prongs for instance), the judge must disqualify the
participant from the rest of the trial. In such an incident, an appropriate
report is to be furnished and sent to the USCA Regional Director, USCA
Director of Judges, and the USCA Judges Committee for determination of