An implant structure includes a contracting mechanism, including a rotatable structure for contracting the implant structure, and a locking mechanism. A rotation tool is configured to engage and rotate the rotatable structure. A longitudinal guide member is removably coupled to the contracting mechanism, configured to guide the rotation tool to the rotatable structure, and includes a distal force applicator. The rotation tool is axially moveable with respect to the guide member. The contracting mechanism is arranged such that the locking mechanism is (a) unlocked when the guide member is coupled to the contracting mechanism in a first state, thereby allowing the rotatable structure to rotate, and (b) locked when (i) the guide member is coupled to the contracting mechanism in a second state, thereby restricting the rotation of the rotatable structure, and (ii) the guide member is not coupled to the contracting mechanism, thereby restricting the rotation of the rotatable structure.