It's a new threshold, and I installed it myself. The old one didn't fit right, and rocked back and forth, and holes were worn through the gasket. Under the old threshold I found layers of old what-we-assume-is-insulation and caulk and general junk. I scraped it all out, drilled holes for anchors in the cement, and securely fastened a shiny new aluminum threshold. And The DOOR STILL CLOSES! The bottom of the door isn't level (but is better since removing a superflous wedge from the bottom), but a new door sweep will fit snugly against the new threshold, and bada-bing-bada-boom! Insulated non-ugly door! Hooray!