Puzzle Sunday (21)

Today on puzzle sunday Burr's. I've created another blog where I want to collect links that I discuss here. Why Burr's? They are cut out (of wood) to practise scaffolding techniques. Remember scaffolding? In this case it's the building of problem solving. What steps will lead to a solution? Can you write down what you tried?
And what I like is that there is a description of a selfmade Burr that costs 1$.
I can visualize Burr making workshops around the world.