A branching stent-graft is deployed such that a distal end thereof is in a branching blood vessel, a proximal end thereof extends into a main blood vessel, and a coupling portion thereof transitions to a partially-radially-expanded state, in which the coupling portion defines a sharp tip at a proximal end of the branching stent-graft. A main stent-graft is transvascularly introduced into the main blood vessel in a radially-compressed state. After the branching stent-graft is deployed, and while the sharp tip remains stationary, the main stent-graft is transitioned to a radially-expanded state, such that the sharp tip punctures the main covering element as the main stent-graft transitions to the radially-expanded state, thereby forming a fenestration in the main covering element. The coupling portion is transitioned to a more-radially-expanded state, so as to form a blood-impervious seal between a branching covering element and a main covering element.
