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.

由于该起重机是固定式的，其塔节与四根固定角钢形接（：对角线接），而角钢的形式又与塔身类型相对应。