This technology includes a device to close a hole in the wall of a large blood vessel or cardiac chamber from the inside out, delivered over a guidewire and through a catheter or sheath. First, the proximal portion deploys within the vessel or chamber and is advanced over a guidewire to oppose the wall and seal the hole. Second, the distal portion self-assembles outside the vessel or chamber upon withdrawal of the guidewire. Deployment of the distal portion anchors the device securely in place.