Crossbow with running nut and a gate that opens on every side
The crossbow's internal release mechanism and a screw-and-gear door device
At the top a large crossbow is drawn whose nut (noce) runs along the cord, with a detail at the right showing how the release mechanism sits inside the weapon. Below is a separate mechanical study Leonardo labels a way for 'a door that opens from every side', drawn as a rectangular frame with two threaded shafts, geared collars and hanging rings. The three brief notes name each element in turn.
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Crossbow whose nut runs along the cord
The upper drawing is captioned as a crossbow that has the nut which runs along the cord, describing a bow in which the catch travels with the string.
The release mechanism inside the crossbow
A detail at the right is labelled as showing the way the release mechanism sits inside this crossbow.
A gate that opens on every side
The lower study is titled a way for a door that opens from every side. It is drawn as a frame with two vertical threaded shafts turning through geared collars, with rings hanging beneath.