Del and Fon,
Actually, those are not what I was talking about. They all mount to the flat top plate or the mast
and would interfere with his light shown in the pix.
What I mean is a U-shaped piece of either strap or rod with two holes in the ends. These holes engage the pin that now supports the shackle of the halyard
block. The block is moved so that its shackle rides on the "U". Something like Ronstan RF1046 or RF1047. Things are often listed as "boom bails" in catalogs.
Hope that this is clearer!