Apologies for being late with the teaser answer tonight, I've had a wee problem with the old 'puter. 
So anyway let's cut right to the chase...
Having shown you this
Then this
And this
Coupled to various references to water, boats, wind-ups, etc.... I kind of thought maybe I'd pushed you all in the right direction.
Happy was on the right track when she said a lock gate... and Spicy was also on track with canal lock... a prize to both these lovely ladies. 
It's a sluice gate mechanism... a wind-up thing! 
For letting water through a dock gate... a lock gate...
Congratulations girls... prize draw is open. 
la_spice
So we get to share a rummage in your drawers - aren't you the lucky one!!!
And with that thought I can now go to bed!
G'night