Uppers:  Cut from selected skins which may be tanned in a variety of ways to produce differing characteristics of grain, substance, softness and durability.
Linings:  These are normally selected from calf or pig skins, which have been tanned to absorb moisture and provide insulation and comfort.
Insole:  Cut from mature shoulders which have been tanned to maximise the qualities of flexibility, suppleness and strength.  Insole shoulder has a high moisture absorption factor – essential for your comfort during prolonged wear.
Sole:  Cut from the back or “butt”.  The tanning process produces leather which is tougher, denser and more rigid than shoulder, increasing resistance to wear whilst reducing water absorption.
Stiffeners:  Cut from belly, the stiffeners and toe puffs are first soaked, allowed to mellow, then skived and beaten to consolidate the fibres.  During the lasting process,  they are sandwiched between the linings and uppers at the toe and around the heel and sides, to help the shoes retain their shape and to provide support and protection for the feet.
Welt:  Made from the best quality shoulder.  The welt is the key component of the hand-sewn shoe because it acts as the flexible interface between the supple upper leather and the sole.
Cork:  Sandwiched between insole and outer sole, the cork provides a cushion which gradually submits to the pressure of the foot and allows an imprint of the foot to be permanently embedded in the shoe.
Welt Thread:  The welting thread is hand-twisted with raw flax impregnated with cobbler’s wax (a blend of tallow, pitch and rosin). Thickness of thread varies from 10-16 strands depending on the type of boot or shoe. The welt stitches bond the insole, lining, stiffener, upper and welt into a strong yet flexible unit.
Sole stitch:  Waxed and twisted from 5-8 strands of flax, the sole stitches attach the outer sole to the rest of the shoe via the welt.   Twisted onto pig’s bristles, the threads are passed through a channel cut in the mellowed sole leather, which is later closed to hide and protect the stitches.
Hand Sewing:  In both welting and sole stitching, the stitches are made by passing the threads, from both sides of the work, through holes made by an awl, ensuring that each stitch is cushioned by the leather (unlike machine stitches which lock around each other at a tight radius, leading to wear through friction – see illustration below).  This hand sewing process, the hallmark of bespoke shoes, dates from the 16th century.

machine-sewn-hand-sewn

Footnote:  Hand sewn shoes are not merely a relic of the past, nor are they a luxury which only the wealthy can afford.  They remain the only practical way of ensuring good-fitting footwear, which, if properly cared for, will prove a sound investment for many years.