To put the file back together, use PIP:

       >PIP newfile.dat=file.001,file.002, ...

       **** NOTE - If the split file is binary, e.g, .COM, .OVR,
       SQueezed or CRUNCHed, you must tell PIP to ignore imbedded
       ASCII end-of-file markers  - ^Z (1A hex) -  for each section.
       For example, if the file SD.COM were split into three sections
       the syntax would be:

       >PIP sd.com=sd.001[OV],sd.002[OV],sd.003[OV]

       If you omit those '[O]'s the output file will almost certainly
       be pure garbage.  The 'V' verifies the transfer and could be
       optional.
                               - Note added by Paul Foote 02/26/87

This concatenates the pieces back into a single file.