lines u03b1 and u03b2 which just as previously described start from the upper end point 24 and 28 respectively and extend differently from fig2 to a maximum 32 on the convexly curved upper face 12 in the direction of an opposite edge 16 of the same puzzle piece the bisector u03bb of the dihedral angle u03b3 formed between the two straight lines u03b1 and u03b2 once again determines the course of the mutually facing edges 16 between the upper faces 12 and the lower faces 14 of the puzzle pieces 10 since curved puzzle pieces 10 do not necessarily have to have a constant radius of curvature over their entire extent and may even be curved oppositely over their extent it is advantageous to define the straight lines u03b1 and u03b2 by the maximum 32 nearest to the mutually facing edges 16 on the upper face 12 of curved puzzle pieces 10 fig4 shows a section through two adjoining puzzle pieces the left puzzle piece 10 of which is curved and the right puzzle piece 10 of which is plane in the case of the curved puzzle piece 10 the straight line u03b1 is determined according to fig3 and in the case of the plane puzzle piece 10 in contrast the straight line u03b2 is determined according to.