Airlocks are another one of those necessary pieces of equipment for every wine maker and homebrewer. S-shaped airlocks are the original airlocks for homebrewing and winemaking. They make it easy to spot fermentation activity, and have no pieces to lose.
Fill with a sanitizer or Vodka and insert in a drilled stopper or the top of a fermentation lid with grommet to vent gases during fermentation.
The advantage of this type of airlock is that they have a smaller chamber so you can more closely observe the CO2 rising and therefore the rate of fermentation. S-shaped locks are best for longer secondary ferments and aging because the liquid in the chamber cannot evaporate as quickly as a 3-piece Airlock. They cannot be cleaned manually if they get dirty during the ferment. That is why many homebrewers prefer 3-piece airlocks for the active portion of the ferment, when the Krausen (foam) from fermentation might be pushed up into the airlock.