Hopefully thie example will show you what i mean.
Essentially, one component is constrained by parameters so that it can only be positioned in certain ways.
I thought about it a bit more, though, and it probably wouldnt be hugely useful as you wouldnt be able to see how the components were constrained untill you tried to move them.
edit: just had another thought, it could be used for some very basic rigging, i'll try ad get an example up and working in a while.
assembly test.skp