How to use MAD calls Spit in drum?

[lock1nout]

picked up one of these older calls and I'm unsure of how to use it. Ive heard a gobbler spit and drum before so Im sort of familiar with the sound. This call is a tad different than most reed calls.

[savduck]

You extend the ribbed plastic end all the way out and then fold it back towards then end where the reed is so that it is shaped like a U. You then blow air sharply over the ribbed plastic end...kinda like blowing across a bottle top to mark it whistle. This gives you the spit......pfttttttttt. Then you blow on the reed end for the drum.