对角线的

The two diagonals of a square cross in the centre.

正方形两条对角线交于正方形的中心。

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

由于该起重机式的，其节四根角钢呈鱼尾形接（译注：即对角线接），而角钢的形式又类型相对应。