Help System (web edition)

For typing of values occuring in consecutive records or simply for
copying existing records and fields, keys F4 and F5 are available.

F4 copies the current field and F5 the entire record. If a marked block
(by alt-F4) exists, the first record of it is used as the model. If
there is no marked block, the previous field (or record) just above is
copied.

If the current field is not empty, F4 has no effect.
Similarly, if the current record is not empty, F5 has no effect.
  S = More information on FILE SHOW