An indwelling assembly includes an inner needle having a sharp needlepoint, an inner needle hub fixed to the inner needle, a hollow elongated outer member in which the inner needle is positioned and movable in a distal direction relative to the inner needle after puncturing the blood vessel to position the elongated outer member at a desired position in the blood vessel, an outer member hub fixed to hollow elongated outer member, a projection removably connected to the outer member hub and configured to be engaged by a finger of the user to apply a force to the projection causing the outer member hub and the hollow elongated outer member to move together with the projection in the distal direction relative to the inner needle and the inner needle hub, and an elongated movable member that is movable relative to the hollow elongated outer member and the outer member hub.
