4 Pieces Packing Problem - Brain Teaser Wooden Puzzle

 The puzzle contains 4 pieces : 2 triangles and 2 trapezoids. One frame is larger than the other. The larger frame is used to store the pieces. Turn it over Notice that this side is smaller and the frame is thicker.  Now, try to fit the 4 pieces in the frame. * Do not use strength.  If you solve it correctly, the pieces will slide in to place smoothly.  Good Luck