The grease ram is useful for forcing grease into a clogged Zerk fitting. The tool looks like a solid steel vesion of a syringe. Fill it with grease or oil, place the tip of the tool against the iput end of a Zerk fiting, and strike the tool with a hammer to induce extraordinarily high hydraulic pressure. If the fitting still does not take oil, you might try a new Zerk fitting first. If that doesn't work, remove the Zerk fitting, dig out as much hardened matter as you can from the threaded port, reinstall and try it again.

You should be able to find one of these at any auto parts store (hopefully), or any decent tool store, or perhaps at a local hardware store.