An anchor device (100, 200, 300, 400, 500) for securing the position of a medical instrument, the anchor device comprising: first and second anchors (140, 240) each having a longitudinal shaft portion and a tine (145, 245) disposed at a distal region of the longitudinal shaft portion, wherein at least a portion of the first and second anchors are deployable through a skin penetration point and into a subcutaneous region along an underside of a skin layer; a retainer base (110, 210, 310, 410, 510) coupled to the first and second anchors and engageable with an external portion of a medical instrument occupying the skin penetration point, the retainer base including an elastically flexible folding region about which the retainer base is adjustable between a first position and a folded position, wherein when the retainer base is adjusted to the folded position, the tines of the first and second anchors are oriented generally adjacent to each other and extend in substantially the same direction, wherein the longitudinal shaft portion of each of the first and second anchors extends distally from a distal end of the retainer base; and a cap (130, 230, 330, 430, 530) that is releasably attachable with the retainer base so as to define a channel therebetween that is sized to engage with the external portion of the medical instrument when the cap and the retainer base are in a first arrangement, wherein the cap is removable from the medical instrument when the cap and the retainer base are in a second arrangement, characterised in that the cap is pivotable in relation to the retainer base during adjustment between the first arrangement and the second arrangement, wherein the cap is pivotable in relation to the retainer base about a pivot axis, wherein the pivot axis is defined by cooperative engagement of either a slot on the retainer base and a projection (132, 232, 331,) on the cap or cooperative engagement of a projection on the retainer base and a slot on the cap. first and second anchors (140, 240) each having a longitudinal shaft portion and a tine (145, 245) disposed at a distal region of the longitudinal shaft portion, wherein at least a portion of the first and second anchors are deployable through a skin penetration point and into a subcutaneous region along an underside of a skin layer; a retainer base (110, 210, 310, 410, 510) coupled to the first and second anchors and engageable with an external portion of a medical instrument occupying the skin penetration point, the retainer base including an elastically flexible folding region about which the retainer base is adjustable between a first position and a folded position, wherein when the retainer base is adjusted to the folded position, the tines of the first and second anchors are oriented generally adjacent to each other and extend in substantially the same direction, wherein the longitudinal shaft portion of each of the first and second anchors extends distally from a distal end of the retainer base; and a cap (130, 230, 330, 430, 530) that is releasably attachable with the retainer base so as to define a channel therebetween that is sized to engage with the external portion of the medical instrument when the cap and the retainer base are in a first arrangement, wherein the cap is removable from the medical instrument when the cap and the retainer base are in a second arrangement, characterised in that the cap is pivotable in relation to the retainer base during adjustment between the first arrangement and the second arrangement, wherein the cap is pivotable in relation to the retainer base about a pivot axis, wherein the pivot axis is defined by cooperative engagement of either a slot on the retainer base and a projection (132, 232, 331,) on the cap or cooperative engagement of a projection on the retainer base and a slot on the cap.