"Bridge" is a badly used term. It came around with professional bodybuilders who would blast a huge cycle, going well over genetic potential, then cruise at a TRT dosage of test. The low dose dbol was thrown in to help maintain the supra-physiological muscle mass while only being on a physiological dose of testosterone. It was a low enough dose that would not down regulate androgen receptors, but it is still suppressive to the HPTA.
People tend to think its a post cycle therapy, or a addition to a post cycle to keep gains. It will only suppress you further and prevent your recovery.