I don't have the Haynes manual for the 122, but in the Volvo P120 - P1800
manual, part 5, page 5-11, Fig. 25 it shows the rear wheel brake unit
with item 3, a guide pin and item 2, a locking washer. The pin is inserted
through the brake plate and through the brake shoe. You put the spring and
the locking washer on it and turn the locking washer 90° to lock it.
Unless either or both the guide pin and the locking washer are badly worn or
corroded, I've not had any problem with them staying where they belong.
Many auto parts stores have generic kits of these pins and washers, some
wit8 springs also. Usually the springs or pins are of the wrong length but
the washers work OK.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma