The default uudemon.poll shell script reads the /etc/uucp/Poll file once an hour. If any machines in the Poll file are scheduled to be polled, a work file (C.sysnxxxx) is placed in the /var/spool/uucp/nodename directory. nodename represents the UUCP node name of the machine.
The shell script is scheduled to run once an hour, before uudemon.hour, so that the work files are in place when uudemon.hour is called.