HP 815MFP - Manual (Page 100)

94 hp designjet 815mfp & scanner 4200
supporting thick originals
To facilitate scanning of thick originals in the extended media
thickness positions it is important to insert the original center
aligned and to help support the original during scanning. This
should be done both at the entrance side and the exit side of the
scanner. Specially designed support tables can be attached behind
the scanner for those who perform a lot of thick media scanning.
see also
how do I copy thick media? on page 7
tell me about the scanner insertion slot on page 59