Bulgarian product designer Konstantin Achkov has created a series of plywood furniture that slots together like a puzzle. All the furniture pieces are held together without glue, nails or bolts. The collection so far includes a round table, bar stool, chair and armchair. Achkov launched his own brand called Tenon to produce this range of furniture, as well as some of his previous works. Stack Furniture was recently presented in Groove and Tenon, an exhibition held during Sofia Design Week 2012.