A stay is provided which comprises a first part (12) including a base (16) for attachment to a wing or to the frame surrounding the wing and an elongate internally threaded tube (24) which is attached to the base (16) in such manner as to be free to pivot with respect to the base. The stay further comprises a second part (14) including a rod (58) with threading compatible with that of the tube (24). A locking element (50) with a circumferential groove is attached to and protrudes transversely from the rod (58) and there is a cylindrical element (40) forming part of a base (34) for attachment to the wing or frame. There is first bore in the element (40) for receiving the element (50) and a threaded second bore intersecting the first bore for receiving a cap screw which enters the groove to prevent withdrawal of the element (50) from the first bore. The second bore is closed by a disc (62) with an Allen key hole opening (64) in it through which the capscrew can be turned.