How to free mates to allow movement in assembly?
At first I was also messed up with this when i was making a model of ATV and had to mate a shocker. Here is the Solution.
First of all open the Main Assembly. As you can see there is a shocker and it is locked.
I right clicked the sub-assembly of shocker and selected Component Properties.
Then in Solve as select flexible.
Click OK and the sub-assembly is flexible.