au, the clamp system on these machines is referred to as "glide bar clamps." I believe there were different ways of doing the crosses on these kinds of machines. Some had two sets of bars and clamps, one of which was shorter than the other, which was used for the crosses. Another system had a rotating base and as you can imagine, it was turned sideways to do the crosses. If you were stringing two piece, the mains would be tied off before you switched over to the crosses. I believe you used a starting clamp to hold the string when switching over to the crosses when doing a 1 piece job. Since the bars were designed to be parallel to the mains and crosses in a standard patterned racquet, they made it awkward to use on fan patterned racquets, so flying clamps would be used on those. I believe the main differences between the various Ektelon models were in the frame mounting system. As racquets changed and got larger and wider with thicker frames the frame mounts had to be updated to accomodate them.