The V2A profile for fastening the center cross of our YAGIs has got a central hole in the "back".
This bolt/screw is inserted through this hole and through the standpipe of the YAGI antenna mast to prevent the cross (the antenna) from turning sideways on the standpipe.
An M6 thread has a diameter of approx. 6 mm.
Therefore a 6.5 mm hole must be drilled through the standpipe (Mast) and secured with a nut, for example.
Of course, such a screw alone cannot protect the YAGI from storm damage. However, it can at least ensure that the antenna does not twist unintentionally on the mast tube in steady winds and small gusts.
Technical specifications:
Hexagon head V2A, M6
Length: 114mm
Fully threaded (DIN 933)
(V2A = stainless steel)