This is a "shell" for a DIY hotshoe to PC socket plug adapter for flash sync.
To heck with spending more than 10€ for a simple piece of plastic, or half but having to wait for the shipment from China.
I adapted the original design adding some holes for cables, used a piece of a spring taken off a pushbutton ballpen, two short cables, and some manual work.

From the pictures you can guess how I cabled it, the trigger for the shot is the gound contact on the hotshoe shorting with the "X" contact, which would be the larger, middle contact.

A bit tricky to assemble, and once you put it on, it needs to be placed correctly otherwise the middle contact won't properly touch the spring (there is not CLICK guiding you into position as commercial adapters).

Tip: you may want to make the spring shorter than what visibile in the picture, as there will be a second cable passing throught the middle hole, so the spring will be contacting an endstop sooner in the form of the ground cable itself.