Methods of Shoe Construction
There are many ways to attach the sole to the upper but commercially only a few methods are preferred. Shoes were traditionally made by moulding leather to a wooden last. Modern technology has introduced many new materials and mechanized much of the manufacture. Remarkable as it may seem the manufacture of shoes remains fairly labor intensive. No matter the type of construction the first stage in construction is to attach the insole to the undersurface of the last. Two main operations follow : Lasting describes the upper sections are shaped to the last and insole. Followed by Bottoming, where the sole is attached to the upper. The process of bottoming will determine price, quality and performance of the shoe.

Stuck on construction

For lightweight and flexible footwear the outsole is stuck to the upper by an adhesive. Bonwelt is a variation with its distinguishing feature being a strip of welting attached by stitching or cementing to the top edge of the insole. The shoe is then flat lasted. This is not a true welt construction wherein the welt is attached to the rib of the insole.

Goodyear Welted Construction

For high quality dress and town shoes the top section (or welt) is chain stitched to the upper and insole rib at the point where it curves under the last. This is supplemented by a lockstitch out seam bonding the welt and outsole. The outsole is then sewn to the welt around the edge.

Theory of Goodyear Welted shoes

Goodyear welted shoes are manufactured by a process invented over three hundred years ago. Later, in the nineteenth century, machinery was developed to help the shoemaker and modern versions of those machines are used to this day. Goodyear welted footwear acquires its name from the long strip of material called a "welt" which is sewn to the upper and insole of the shoe. The outsole - generally referred to as simply the sole - is attached separately to the welt. This extra part of the construction gives Goodyear welted shoes their strength, flexibility and comfort.

The benefits of Goodyear welted footwear include :

    Exceptional  Comfort - The  cavity  created  by the inseam between   the inner and outer sole is filled with a flexible compound
     CORK) that quickly moulds to the shape of the wearer's feet.

    Easy to Repair - As long as the uppers  remain  sound,  it is straightforward to re-sole a pair of worn welted boots or shoes by
     sewing  new  ones  to  the  existing  welts,  to  give  them  a  life  expectancy  of  20 years or  more. This  can  be done either by 
     a competent repairer or by having the shoes rebuilt by the factory that made them.

    Insulation - The  sandwiched  compound  between  inner  and  outer soles  provides  thermal  insulation  and  protection from
     uneven surfaces for added comfort.

    Flexibility - The Goodyear welted construction is highly adaptable  to  almost  every  style  of  shoe, for  every  walk of life, which
     enables shoe makers to quickly respond to trends in both dressy and young fashions.

    Strength - Comfort  combines  with durability  in  Goodyear  welted  footwear  to  provide  incomparable  strength,  outstanding
      performance and enhanced shape