对角线的

The two diagonals of a square cross in the centre.

正方形两条交于正方形的中心。

As the crane is static the mast sections are directly fishplate onto the 4 fixing angles corresponding to the mast type used.

于该起重机是固定式的，其塔节与四根固定钢呈鱼尾形接（译注：即接），而钢的形式又与塔身型相应。