Round-rail technology has been honed to near perfection over the past 60 years and square profile rails a respectable 35. Both have definitely matured and most of the inherent design problems have long been ironed out. Materials have improved dramatically and the fi nest engineers have shaped linear rail technology into an “exact science.” Most problems arise from misuse and misapplication. And the main reasons for misapplication often come from a personal bias or prejudice, a miscalculation, or an esthetic judgment. That is, a relatively small linear profile rail might fi t the load, speed, and every other requirement just fine, but when it’s mounted to the machine, a discerning eye might conclude that it looks feeble, definitely undersized.