Here is nice little time saving tip for you CATIA V5 users out there. Many times when you are starting a sketch, you will find that it is too small or too big, and as you add constraints and modify them, your sketch becomes misshaped. Therefore, you need to scale all lines, arcs and circles with the constraints already on the sketch. To do this, use the scale without the duplication turned on. The nice part of doing this is that all the constraints will scale up or down at the same time and in the same ratio. This timesaving trick prevents you from fiddling with the sketch to get it close to the size you need. This is especially helpful on sketches with a lot of arcs and circles with tangencies. It also prevents complex sketches from turning red (with an error), because geometry relations need to increase at the same ratio simultaneously to retain shape integrity. Hope this helps!