verb
attach
uh-TACH/əˈtætʃ/
To join one thing firmly to another.
The craftswoman attaches a buckle strap to the bag.

Etymology
Old French atachier covered both fastening and arresting. English first used the word for legally seizing property, then for the physical joining or connecting familiar today.
In context
Step four is to attach the seat onto the slide bar and the slide bar onto the main frame.
More examples
- Please attach your resume when you reply to the email.
- The army attached a medic to the engineering unit.
- He grew deeply attached to the old house.
Forms
attach · attaches · attached · attaching
attachment noun — A joining, added part, or emotional bond.