The guard check and guard face gages in frogs shall be within the limits prescribed in the following table -

Class of track Guard check gage The distance between the gage line of a frog to the guard line 1 of its guard rail or guarding face, measured across the track at right angles to the gage line 2, may not be less than - Guard face gage The distance between guard lines 1, measured across the track at right angles to the gage line 2, may not be more than - Class 1 track4′6 1/8″4′ 5 1/4″ Class 2 track4′6 1/4″4′ 5 1/8″ Class 3 and 4 track4′ 6 3/8″4′5 1/8″ Class 5 track4′6 1/2″4′ 5″ 1 A line along that side of the flangeway which is nearer to the center of the track and at the same elevation as the gage line. 2 A line 5/8 inch below the top of the center line of the head of the running rail, or corresponding location of the tread portion of the track structure.