Another shot of the topmast fid control. The 6mm control lines emerge from the sheave box which house two small sheaves arranged to lead the control lines to fore and aft of the fid. Pulling the fore control line slides the fid forward and into the slot in the after face of the topmast so securing it when up; the after control line pulls the fid aft and clear of the topmast allowing it to be struck. Works a treat! The four holes in the 3" oak trestletrees mark where the 11' wide spreaders (6" x 1 1/4") bolt on. At the bottom of the photo you can see a slot where the throat halyard block strop passes through. Conventionally, this block is hung off a crane bolted through the mast above the hounds but is a source of rot in masts. I have designed the trestletrees to overhang aft an amount equal to the throat block on the gaff so keeping the tackle vertical just as a crane would do. The served wire strop passes round the front of the mast, similar to a shroud, through the slot which is split for ease of reeving, and finishes with two thimbles for shackling to the top throat block. Another advantage of the strop is to allow the top throat block to swivel more when off the wind. A disadvantage to this system is that the hounds are further above the bending force of the gaff jaws because of the fleeting required in the throat tackle. The mast is just under 8" dia. here and the topmast 6" D shaped to line it up when hoisting. (The topmast is from a telegraph pole)