The bed leveling adjustment screws on my Prusa I3 printer use a cap screw, spring and a wingnut. In order to adjust the screw, you have hold one part while turning the other. This part and a 3 mm hex nut replaces the wingnut and allows you to adjust the bed leveling screws using a hex driver on the cap screw without having to hold onto a second part.
There are a couple versions. The one with the long arms is the easiest to print and install. The one with one shortened arm was required to avoid interference with the frame and collars on the smooth rods of the Y axis. The short arm lies along the X axis, the long arm along the Y axis.
The keeper with the short arm needs a mirror image copy along with the one shown in order to fit on both sides of the print carriage. Repetier and probably others will easily generate a mirror image copy.
The keeper with the short arm requires support, which can be difficult to remove from the hex nut recess. The one with the long arms requires no support.
Why it looks the way it does:
On my Printer, the hole pattern of the carriage does not match the hole pattern of the bed heater, therefore the adjusting screws are at an angle. The cone provides a pivot point to accommodate the misalignment of the screw connecting the two pieces. The arms and the pads that protrude from them press against the print bed carriage and prevent the nut from turning. The thickness push-out of the pad at the end of the arm provides some tension to keep the nut from turning if the hole pattern is such that both arms don't contact the carriage.
UPDATE 12/3/16
There are a couple things that can theoretically have a positive effect on the bed adjustment and are easy to do.
They include polishing the ends of the springs so they don't have any wind-up torque stored during adjustment, and adding some locktite (blue) to the screw thread to discourage drift.
The ends of the wire spring are cut off square, thus leaving an edge that can dig into the material they rest upon and possibly store some energy when the screw is rotated. Polishing them with a fine stone removes the edge and the tendency for wind-up.
Adding some blue locktite to the screw makes the screw less likely to turn in the nut unless you are the one turning it. Apply only a small amount of Loctite. Let is set a couple days and then turn the screw to break the hold of the Loctite. Hold onto the keeper to prevent it turning (and breaking) when you first turn it.