Assembly can mean many things to different products.  From riveted assembly to component weldments; light mechanical installation to UL 508 listed electric control panels; plumbing and wiring to full product integration.

Please see below for a few project examples, and let us know if you're project is similar; or requires something entirely different.  We'll be happy to evaluate the most effective approach with you.
Electrical Assembly UL 508 Powder Coated Panel

Steel Fabrication Cabinet 2

Steel Fabrication Cabinet