I was watching the following video  http://www.solidworks-apac.com/2009/12/21/how-to-animate-a-spring/ and need some help. At about 2 minutes in is the section on "putting spring into action" where the spring can be compressed or extended in relation to how the part moves. I take it that the spring is an existing part inserted into the assembly. Now when the spring is edited to make it Coincident is the part that gets me. Is the spring edited in the assembly or is something else done?? When I go to edit the spring all the other parts become visible as what normally happens, however in this video the other parts don't change. Its almost as though the relationship is added within the assembly. He does say "first edit the sketch part", I'm just a wee bit lost with it and know its probably a simple explanation that's obvious so any help is welcome!!