The structural design of the satchel is the most important because it determines the performance of the package in terms of practicality, durability, comfort and many other aspects. The function is not the more the better package, the overall design is simple and practical to avoid fancy. The comfort of a package is basically determined by the design structure of the backpack system. The backpack system usually consists of a belt, a belt and a back pad. A comfortable bag should have a wider, thicker and arbitrarily adjustable belt, a belt and a back pad. The back pad is best with a sweating and ventilating slot. Material includes two aspects of fabric and component. Fabrics should usually be wear-resistant, tear proof, waterproof and so on. The more popular ones are Oxford nylon cloth, polyester staple fiber canvas, cowhide and genuine leather. The components include the waist buckle, all zippers, shoulder straps and chest buckles, cover and bag fasteners, fastener fasteners, etc., which are usually metal and nylon, and should be carefully selected with your eye when purchased. The workmanship refers to the stitching quality of the shoulder belt and the bag body, the fabric, the cover and the bag. To ensure the necessary stitching, the stitches should not be too large and loose.