This is made of lap joints and bridle joints and completely fancy. The red marks indicate the “waste.” This is Jay’s example from his 15 minute demonstration.
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lap joints. Will you look at the straight sawing of this wood? He always makes it look so easy. (wait til you see my version!)
He has the ends sticking out so that he can make it nice and even later on. 
This one is missing the bottom half of the lap joint, but you can see how top one fits inside the bridle joints.
I think the red marks are from the red marker he uses to mark the waste… or blood. I’m not sure. But it is Jay doing it so I think it’s the former.