Apparatus (20) is provided for use with a guidewire (12). The apparatus includes a guide tube (22) having a guidewire-engaging portion (122) and a slit (28) extending proximally along a wall of the guide tube, from a distal end (32) of the tube, a proximal end (29) of the slit being located distally to a proximal end (30) of the tube. A first stent (52) surrounds the tube and is advanceable together with the tube into a lumen of a subject, the first stent being slidably advanceable off the distal end of the tube; and a second stent (54), proximal to the first stent, surrounding a proximal portion of the tube, and advanceable off the distal end of the tube into the lumen, and placed alongside the first stent subsequently to advancement of the first stent off the distal end of the tube. Other applications are also described.