<human>: Can you succinctly summarize the text in 1-3 sentences?

For the last few weeks my kung fu instructor and I have been working on knife-fighting scenarios, specifically being attacked with a knife while unarmed. He likes to surprise me with cheap shots when I'm not paying attention to the dummy knife or when I think the exercise is over - just to make the point that you never know when someone is going to pull a knife on you. Now, I'm generally on my guard when he's got a dummy knife in his hands.

Today, though, the mailman arrives in the dojo in the middle of our lesson and my instructor lays the dummy knife on the mat and goes over to sign for the package. As he opens the box I approach to see what cool new thing he's ordered for the dojo, at which point he whips around and lunges at me with the *huge dummy commando knife he's just gotten out of the box.* I react as I've been trained, grab his arm and flip him onto the floor right at the feet of the stunned mail guy.

My instructor explained that he knew roughly when the mailman usually arrived on his route, ordered the knife, and scheduled my lesson accordingly. All just to surprise me.
<bot>: My kung fu instructor ordered a dummy knife through the mail so that it would arrive during my lesson and he could attack me with it.