Have you ever seen anything like these before?
They are a primitive form of sash lock, often found on historic or vintage wooden windows. The one on the left is a simple, turned oak dowel, while the one on the right is forged from iron, and is much fancier and more substantial:
A small diameter hole is drilled through the meeting rails of the interior (lower) and exterior (upper) sashes, but without going all the way through the exterior sash. With the window closed, the lock is inserted all the way into the hole, thus preventing the interior sash from being raised.
Furthermore, by drilling a series of matching holes along the length of the upper sash’s stile, the lock can be used to hold/lock a raised lower sash in place, when the window is to be kept open. Many old single-hung windows incorporate something like this, since the use of counter weights or springs to hold windows open simply hadn’t been invented at the time of their construction.
A nice property of the iron lock is that the twisted part of the shaft holds very tightly against the wood, as long as the hole is just the right diameter. So, if you have two on each side of the window, they can hold the meeting rails together very tightly and provide a good air seal, just as a modern sash lock does. Hence, it’s the more energy efficient of the two forms of primitive sash lock!