required by such a mechanism prevents the fingers from being positioned close enough to provide top efficiency of operation interference with the rotating drum surface is another problem which limits the closeness of the interposer to the transfer point i e the point where the paper a actually meets the drum or printing device stopping and starting the paper for normal amounts of time would tend to cause the front edge of one sheet to crash into the rear edge of the sheet in front of this first sheet belts are inherently expensive to fabricate maintain and utilize as seen in fig3 of the drawings the desired path for the interposer is not one easily obtained by conventional registration finger motion i e rotating devices or fingers on a belt however by synthesizing an appropriate four bar linkage the coupler curve can be used to provide the desired motion the concept of a four bar coupler curve interposer action represents a novel improvement over existing methods the synthesis of such a mechanism produces a four bar interposer linkage such interposer provides all the desirable features previously listed also its speed can be tailored to provide the proper interception action and the dwell portion beneath the paper path can be designed so that the nose to tail distance window resulting between sheets is minimal which is an important factor in throughput of cut sheet printers having a given print speed as noted by reference to fig3 an acceptable maximum mechanism envelope has been previously calculated in order most efficiently to take advantage of the available non interfering space between the paper feed.