On the beach or in the backyard always be ready to whack your brother with style.

These are Warrior Gear compatible handle mounts for making shields. The mounts are also compatible with the longer handles from the hand and a half sword.

If you are interested in designing a compatible part the threading is M26x1.5 and the flats of the polygon hole are at the diameter of the PVC pipe 21.5mm.  If your tolerances end up too tight you can scale the x and y directions by 101% while keeping the z direction at 100%. that will make it a bit wider without changing the pitch of the threading ( assuming z being the axial direction ). 

Disclaimer: Use at your own risk.  There is always some danger in whacking each other.