A stent-graft (20) is provided, which is configured to initially be placed in a delivery shaft (40) in a radially-compressed state, and which comprises a support structure (36) and a covering element (38). The support structure (36) has proximal and distal ends, and is shaped so as to define at least a coupling portion (30), which 5 is configured to transition to a partially-radially-expanded state upon deployment of the stent-graft (20) from the delivery shaft (40), in which state the coupling portion (30) defines a sharp tip (34) at the proximal end of the support structure (36). The covering element (38) is securely attached to and covers at least a portion of the support structure (36). A 10 coupling-end expansion tool (100) is configured to transition the coupling portion (30) from the partially-radially-expanded state to a more-radially-expanded state. Other embodiments are also described.
