In the past, I have faked weldments in assembies.  I was sold yesterday of the advantages of making weldments at the part level.  I understand how to make weldments out of 3d sketches then specifying the structural members, but I am not clear on how to use one of our companys parts (for example, we have a custom gusset that has holes in it for a takeup unit).  Can someone please explain the process of doing this to me?

*Just so you know, the screenshot I attached is an assembly and I want to make it a weldment (part).  There are 3 angle irons, and 2 different custom gussets that our company uses.

Thanks in advance!

-Cliff