points are not selected when making a spring mechanism

[SJ_9842470]

Hi, I was trying to make a simple spring mechanism for school project

When creating this, I faced a problem that two pairs of dots are not simultaneously selected.

As shown in the attached figure, pnt0 and pnt1 were set on the top and bottom of each part, respectively.
I tried to select the other point by pressing and hold Ctrl key , but it didn't even work.
How should I solve this problem? I don't know what the problem is.

[Haydena · Accepted solution]

Dear SJ

I found out why we cannot select the second point for the spring mechanism.

Your packaged component must be an assembly component that is not fully constrained.

Please find the attached image.  Thank you!