An attachment device for anchoring to tissue of a patient, the attachment device comprising at least one body element provided with a base surface for contacting the tissue of the patient when the attachment device is attached to said patient, and an anchoring portion comprising: a first piercing member for anchoring the device by insertion of a first insertion portion, comprising at least a pointed end part of the first piercing member, into the tissue of a patient the first piercing member being attached to, and supported by, a first support body; a second piercing member for anchoring the device by insertion of a second insertion portion, comprising at least a pointed end part of the second piercing member, into the tissue of a patient, the second piercing member being attached to, and supported by, a second support body; wherein the first and second support bodies (12, 16) are relatively pivotably coupled for relative rotational movement, between an open position of the anchoring portion in which the anchoring portion is inoperative and a closed position of the anchoring portion for anchoring the device to the tissue of a patient; wherein the first support body comprises a first control portion via which a force can be applied to effect rotation of the first support body relative to the body element and the second support body; wherein the second support body comprises a second control portion via which a force can be applied to effect rotation of the second support body relative to the body element and the first support body; wherein the anchoring portion is operable from its open position to its closed position by drawing together said first and second control portions to effect relative rotation of the first and second support bodies about common axis; and wherein in the open position of the anchoring portion the bottom surfaces of the first and second support bodies are parallel to the base surface of the body element and the first and second piercing members do not extend downwardly from the bottom surfaces of the first and second support bodies. a first piercing member for anchoring the device by insertion of a first insertion portion, comprising at least a pointed end part of the first piercing member, into the tissue of a patient the first piercing member being attached to, and supported by, a first support body; a second piercing member for anchoring the device by insertion of a second insertion portion, comprising at least a pointed end part of the second piercing member, into the tissue of a patient, the second piercing member being attached to, and supported by, a second support body; wherein the first and second support bodies (12, 16) are relatively pivotably coupled for relative rotational movement, between an open position of the anchoring portion in which the anchoring portion is inoperative and a closed position of the anchoring portion for anchoring the device to the tissue of a patient; wherein the first support body comprises a first control portion via which a force can be applied to effect rotation of the first support body relative to the body element and the second support body; wherein the second support body comprises a second control portion via which a force can be applied to effect rotation of the second support body relative to the body element and the first support body; wherein the anchoring portion is operable from its open position to its closed position by drawing together said first and second control portions to effect relative rotation of the first and second support bodies about common axis; and wherein in the open position of the anchoring portion the bottom surfaces of the first and second support bodies are parallel to the base surface of the body element and the first and second piercing members do not extend downwardly from the bottom surfaces of the first and second support bodies.