guess the tool!

[Shedhand]

could be a simple lever from a device to transfer flow of liquids - say irrigation - a wooden shaft is rebated to match the open end of the steel top then a "paddle" fitted to the bottom of a wooden shaft which swings between two or more water channels to direct water flow. Prolly drive a tractor or horse in an irrigated field and tap the lever with stick or a foot..
hmmm. might patent that idea???

[fenderbelly]

Now that you've said that, the last place i was at there was a similar gadget ( but plastic ) in the septic system.

The pipe coming from the tank to the soakage pit split into two pipes with the gadget at the junction of the split, as this was 4 or 5 feet down there was a shaft coming to the surface inside a piece of stormwater pipe to operate the thing.

Cheers Fred