Harmar Mobility AL001 - Manual (Page 6)

Next loosen the bolts on the anti-tilt lock bracket. (There
should be grooves where the bolts were tightened against the hitch
receiver)
This procedure is required only during the initial installation of
the anti-tilt lock bracket as for the grooves will ensure repeated
relocating of the anti-tilt lock bracket. Now pull the carrier out to its
final location and install the hitch pin. Return the anti-tilt lock
bracket to the location securely against the hitch receiver and
torque the bolts.
THE BOLTS SHOULD FALL INTO THE
GROOVES CREATED EARLIER IN THIS
PROCEDURE.