reference stops

[DariaVictorovna]

Пожалуйста, помогите перевести
Выражение встречается в следующем контексте:
The clamps are independent from the zero of the machine and they have the possibility to pull the panels against the reference stops to grant a perfect alignment of the piece. This feature is very important when the machine is loaded manually because the operator can improperly draw the panel near to the reference stops generating boring errors.

Заранее спасибо