Stable and Durable Type Mast And a Reliable Choice for Oil Drilling 1. The mast type is generally divided into A type, K type (front opening type), tower type and mast type, etc. 2. Type A mast, the thigh section is rectangular or = angular, etc. The bearing capacity and local stability are relatively good. Each section is connected by pins. The mast is installed in a low position, and the herringbone frame is used to rely on the power of the grain car as a whole. 3. Type K