Still used coming back to San Jose on the Permanete job from Vasona Jct. If you need them coming down Donner, Grass Lake, Cuesta, ect. apply to Omahaha.

The idea behind retainers is that once you make a brake pipe reduction, leakage has adverse effects on it: Brake Pipe leakage causes an increase in a brake application and Brake Cylinder leakage just the opposite (essentially a release). Eventually you have to recharge the system to go back to square one. The job of the retainer, when "turned up" is that it prevents the air pressure from exhausting from the brake cylinder, so that when you recharge the system, which is the same as releasing the brakes, the brakes don't actually release (and you don't run away down the hill). The use of retainers on grades has been essentially done away with by pressure maintaining.