English to Russian Tech/Engineering Engineering (general) проектир-е конвейера

Добрый день! Подскажите, пожалуйста, что за rathole -это типа отверстия/кармана?
The top window allows the basic material data to be entered. This includes the material density, stacking angle, reclaim angle, and rathole angle.
Ratholes can be used for circular reclaim points as well as liner slots. The rathole height is used in conjunction with the rathole angle

Спасибо!