A removable blind fastener, comprising a) a first tubular element with a head portion at one end, a guide portion at the other end, and a dowel portion wherein the guide portion has a plurality of guides (24, 26, 28) extending away from the head end of the first tubular element in a direction parallel to the central axis of the first tubular element, the space between the guides defining guide channels, and wherein parts of the first tubular element between the guides define sills (34, 36); b) a second tubular element having a threaded portion and an arm portion, the threaded portion having an internally threaded aperture along the central axis of the second tubular element, and the arm portion having a plurality of outwardly biasable resilient arms (30, 31, 32) extending away from the threaded portion in a direction parallel to the central axis of the second tubular element, wherein the number of arms is equal to the number of guide channels provided on the first tubular element, and wherein the arm portions of the second tubular element each have end portions (30a, 31a, 32a); the removable blind fastener further comprising; c) an elongate screw member having a head portion and a threaded portion, wherein, in use, the screw member is located within the first tubular element and the second tubular element in such a way that the first tubular element, second tubular element and screw member are co-axial, and whereby the head portion of the screw member is located within the head portion of the first tubular element, and the threaded portion of the second tubular element is threaded onto the threaded portion of the screw member, such that the arms (30, 31, 32) of the second tubular element can engage with the guide channels of the first tubular element; the removable blind fastener characterised in that each of the end portions (30a, 31a, 32a) of the arms (30, 31, 32) of the second tubular element are thicker than the rest of each arm, to define a recess behind the end portions of each arm, wherein the thickness in a direction perpendicular to the central axis of the second tubular element of the ends of the arms determines the distance that the end portions are biased away from the central axis of the second tubular element in use; and wherein the removable blind fastener is arranged so that: (i) rotation of the screw member in a first direction causes movement of the second tubular element towards the first tubular element in a clamping direction, this movement causing the arms (30, 31, 32) of the second tubular element to move along the guide channels of the first tubular element and engage with the sills (34, 36) of the first tubular element, whereby continued rotation of the screw member causes the arms of the second tubular element to bias outwardly, away from the central axis of the second tubular element against the sills of the first tubular element and then slide along the dowel portion; and (ii) rotation of the screw member in a second direction causes movement of the second tubular element away from the first tubular element in a releasing direction. a) a first tubular element with a head portion at one end, a guide portion at the other end, and a dowel portion wherein the guide portion has a plurality of guides (24, 26, 28) extending away from the head end of the first tubular element in a direction parallel to the central axis of the first tubular element, the space between the guides defining guide channels, and wherein parts of the first tubular element between the guides define sills (34, 36); b) a second tubular element having a threaded portion and an arm portion, the threaded portion having an internally threaded aperture along the central axis of the second tubular element, and the arm portion having a plurality of outwardly biasable resilient arms (30, 31, 32) extending away from the threaded portion in a direction parallel to the central axis of the second tubular element, wherein the number of arms is equal to the number of guide channels provided on the first tubular element, and wherein the arm portions of the second tubular element each have end portions (30a, 31a, 32a); the removable blind fastener further comprising; c) an elongate screw member having a head portion and a threaded portion, wherein, in use, the screw member is located within the first tubular element and the second tubular element in such a way that the first tubular element, second tubular element and screw member are co-axial, and whereby the head portion of the screw member is located within the head portion of the first tubular element, and the threaded portion of the second tubular element is threaded onto the threaded portion of the screw member, such that the arms (30, 31, 32) of the second tubular element can engage with the guide channels of the first tubular element; (i) rotation of the screw member in a first direction causes movement of the second tubular element towards the first tubular element in a clamping direction, this movement causing the arms (30, 31, 32) of the second tubular element to move along the guide channels of the first tubular element and engage with the sills (34, 36) of the first tubular element, whereby continued rotation of the screw member causes the arms of the second tubular element to bias outwardly, away from the central axis of the second tubular element against the sills of the first tubular element and then slide along the dowel portion; and (ii) rotation of the screw member in a second direction causes movement of the second tubular element away from the first tubular element in a releasing direction.