In an aspect, a kit of parts is provided for a check arm keeper, which includes a keeper housing having a mounting bracket and a cartridge-mounting portion, and a plunger cartridge that includes a plunger cartridge housing mountable to the keeper housing, a plunger slidable in the plunger cartridge housing, and a plunger-biasing member positioned in the plunger cartridge housing to urge the plunger out from the plunger cartridge housing. The plunger has a first engagement member and the plunger cartridge housing has a second engagement member. The engagement members cooperate to retain the plunger in the plunger cartridge housing against a biasing force of the plunger-biasing member when the plunger cartridge is free from the keeper housing. Mounting of the plunger cartridge housing holds it in a selected position relative to the keeper housing and drives the plunger to a position in which the engagement members are spaced apart.