The operation is very simple: TOP Layout, when loaded, is able to intercept any loading operation of parts from external libraries. In this phase, TL controls the name of the .DWG file loaded and the name of the folder that contains it and checks for a sheet with the name of the folder inside the counting sheet. If the sheet is found, TL analyzes the DWGNAME column for a match with the name of the loaded footprint.

If there is correspondence, it triggers the TL allocation mechanism: all values in the row intercepted are assigned as part attributes (unless the first letter is not a UNDESCORE symbols (_). In this case, the attribute is not assigned.