Rein Check is a job that involves the inspection of reins, which are straps used to control horses. The term is often abbreviated as BIT, which stands for Bridle Inspection Technician. A Rein Check technician is responsible for ensuring that the reins are in good condition and free from defects. They must also check for any signs of wear or damage that could affect the performance of the horse. The technician must also be knowledgeable about the different types of reins and their proper use.