Подскажите, пожалуйста, что такое Lock Link Bar или Tandem Lock Link Bar?

Тематика: окна и двери

Avoid locating screws near Tandem Lock Link Bar.
Screws must be located to the interior side of Lock Link Bar, at 15° to avoid hitting extension jamb kerf.
For Vertical Joins, avoid locating screws near Tandem Lock Link Bar.
Screws must be located to the interior side of the Lock Link Bar at a 15° to avoid extension jamb kerf.

Спасибо!