49 C.F.R. § 236.743 Dog, swing.
Title 49 - Transportation
A locking dog mounted in such a manner that it is free to rotate on a trunnion which is riveted to a locking bar. Element, contact. See receiver, §236.788.
Title 49: Transportation
PART 236—RULES, STANDARDS, AND INSTRUCTIONS GOVERNING THE INSTALLATION, INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES
Subpart G—Definitions
§ 236.743 Dog, swing.

