He walks to the passageway of the house, picks up a rock, and cuts
through one of the sticks in the doorframe, then one on the other
side. He ties the whip between the two, forming a taut tripwire. Then
he signals to you to get on the other side of the doorframe.
Event tripwire is set!
He looks at you with a bit of fear in his eyes. "Where did you
learn..?" To be honest, you're not sure yourself, except that
your grandfather did put you through quite a bit of training. Then he
recovers himself, and stands upright, suddenly not seeming so frail.
"Let me have this whip, Yynas, I have an idea." You pass it
to him.