I got this. That is wood. 
My first thought was chair. But it isn’t symmetric, and the dimensions seem like they might be like a 123 block. So my final answer is some kind of clamp. 
Mahogany plywood to be precise.
Far too nice to be clamps then…
Kayak seats?
Close 
A chisel and a hammer?..
hard covers for kayak ?
Pizza Paddles - for small & large. If it was me, I would make the handles a bit longer.
I would also let them bake a bit longer so you don’t need the hammer & chisel to get them off the paddle
So easy, his and her’s ping pong paddles.
Ding Ding Ding
Just dug out a kayak that I built 25 years ago and decided to restore it after some poor storage for a long time.
The varnish was a total loss but it’s still structurally ok so I’ll see how it turns out.
The hatches on the other hand were shot:
Luckily I still had printed plans for the parts and a slight improvement of tools since last time:
There is no way they were shot… not a single hole in either one…
Oh…
Different kinda shot.
Beautiful kayak btw
Here are some vintage pics.
I watched a lot of this boat as it was getting cut by a mystical machine called a cnc at clboats which is near my house. I had never heard of one before back in 97’
Take a fallen tree and suspend an LR3 over it to carve out the kayak from scratch. That would be something.
I think that would be called a surfboard with the LR3’s Z travel.
They call them stand up paddle boards now.