49 C.F.R. § 236.742 Dog, locking.
Title 49 - Transportation
A steel block attached to a locking bar or tappet of an interlocking machine, by means of which locking between levers is accomplished.
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
§ 236.742 Dog, locking.