The fixed set of pulleys (called sheaves) located at the top of the derrick or mast, over which the drilling line is threaded.
位于重型井架或桅架式井架顶部的固定的滑轮组（称之为滑车轮槽轮），通过该滑轮组钻井钢丝绳进行穿绳。
2
In the present study, rabbit mesentery was fixed in three different fixatives and stained with thionine and thionine-toluidine blue respectively in order to find a good method to display mast cells.