This is how Woodman describes the Steerer Clamps they sell.
http://www.woodmancomponents.com/Web...%88%2002:57:26
The Steerer Clamp holds the fork and threadless headset assembly together when you remove your bicycle’s stem for shipping, transport or storage. Typically, if you remove your stem, your threadless fork and headset will come apart and you risk losing small parts like bearings or spacers. Furthermore, when it’s time to reassemble the bike, properly adjusting the headset preload typically requires a qualified mechanic. Our Steerer Clamp eliminates all of these problems. Simply install the Steerer Clamp beneath your stem, have a qualified mechanic adjust the headset preload, and then tighten Steerer Clamp. All that’s required for reassembly is to align the stem with the front wheel and tighten it to the correct torque specification.