49 C.F.R. § 236.337 Locking faces of mechanical locking; fit.
Title 49 - Transportation
Locking faces shall fit squarely against each other with a minimum engagement when locked of at least one-half the designed locking face.
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 C—Interlocking
Rules and Instructions
§ 236.337 Locking faces of mechanical locking; fit.