Dyson DC24 Swivel Lock (Ref: 20)
This is the lock arm that come around the front of the machine and sits just above the cleaner head. Its designed so that when the machine is lifted to be carried it locks the head in place.
If your head tilts to the side when being carried then it may be that this part needs replacing. Will fit all DC24 models, although yours may be a different colour. Does not include the small spring, so please keep your old one safe