Has anybody got Nagios to accept SNMP traps?

I've got Nagios running quite well (on a 64 bit Ubuntu server), and it polls Linux and Windows servers using NRPE. So far so good.

However, I want Nagios to accept SNMP traps from the Windows program 'Trapgen' which we use to flag when things go wrong with our scripts.

I've searched high and low, but have been unable to find a coherent, complete document explaining how to do it from start to finish. It's driving me nuts.

I've installed and configured snmptt (trap translator), the SNMP daemon is set to not log but to use the trap translator.

This is the best document I could find: SANJAY WILLIE'S Human Language Technology: Nagios Receive SNMP Traps (with SNMPTT)