the keel on the ground - ignore the ladder

11-00 hrs: The keel runs up and down on runners on each side - the red arrow points to one of them. The blue strap winds the keel up and down from inside the boat, through the slot at the bottom ( a red arrow points to this). 

What stops it falling out? Answer - nothing apart from the strap. It may have rested on the fitting that holds the slot gasket in place.

The design is for a nylon bush to be fitted at approximately the place of the round red circle. This then catches on a ridge in the keel casing and stops it falling out. Nice. But - mine did not have one. It does now,  the Tidemill staff made and fitted one before the keel was put back.

But - you may say - how do I get it out next time I need to inspect it? Good question - the nylon bush unbolts through holes in the keel case inside - necessitating the removal of a lot of woodwork and the galley to get at it - so a non-trivial thing to do. But feasable.

At least I am not going to have the keel fall out of the bottom next time I do something daft. And I better understand the whole mechanism as a result of all this.