Basic Maintenance: Brake Fluid

[peterbaron]

..... I'm trying to replace the rear brake fluid but no fluid is moving through the tube connected to the loosened nipple as I depress the rear brake pedal repeatedly.  There is plenty of fluid in the reservoir.

....

but is the brake pedal hard, soft, sinking and going down when the nipple is loosened or..???
Was the robber cap missing from the bleeder??