Подскажите, пожалуйста, что такое ribbons flush в тематике окон и дверей?

Контекст:
Align pencil marks.
Align ribbons flush at ends and clamp together securely.
Fasten using 1-5/8" screws inserted into predrilled holes through Side Jambs.

Спасибо!

Align (кого/что?) ribbons (каким образом?) flush at ends

т.е. flush - наречие

adv.
1. So as to be even, in one plane, or aligned with a margin.
2. Squarely or solidly: The ball hit him flush on the face.