Think of the space shuttle orbiter as a big puzzle with each of its heat shield tiles a puzzle piece.
All space shuttle thermal protection system (TPS) tiles are assigned a serial number identifying where on the orbiters they are to be installed. Each tile is individually made to fit a specific location.
Tile serial numbers normally consist of four segments, the first three separated by dashes, such as:
The first two elements of the serial number are letters 'VT' or 'VO'. The 'V' is for Vehicle, the 'O' is orbiter.
The second set of six digits is the location on the vehicle. The following table provides basic locations.