A useful technique for studying microtubule motors is to attach them by their tails to a glass cover slip (which can be accomplished quite easily because the tails stick avidly to a clean glass surface) and then allow them to settle. Microtubules may then be viewed in a light microscope as they are propelled over the surface of the cover slip by the heads of the motor proteins. Because the motor proteins attach at random orientations to the cover slip, however, how can they generate coordinated movement of individual microtubules rather than engaging in a tug-of-war? In which direction will microtubules crawl on a “bed” of kinesin molecules (i.e., will they move plus-end first or minus-end first)?