Measure the distance from the sole of your foot to your knee when standing erect.
Cut two steel rods to a length roughly 12 inches longer than this measurement.
Sharpen one end of both metal rods with an angle grinder. Test the point by striking the sharp end of the rod against a piece of wood. If the tip breaks off when pressure is applied to it or the rod is unable to puncture the wood, adjust the angle of the point.
Heat one rod at a point the length of your shin away from the blunt end, using a blow torch. Wearing thick work gloves, bend the rod into a right angle at this point once the metal is soft enough.
Heat a section of the spiked end, the width of your foot away from the bend. Angle it upward and then horizontally again, forming a sort of stirrup for your foot. This will add extra security.
Repeat the heating and bending operation on the second rod.
Put on a pair of hiking boots and place the climbing spikes in position, with the points facing outward, the stirrup-part under your arch and the long section extending up the outside of your leg. Lash the vertical support and the stirrup portion to your leg with sturdy mountaineering straps before climbing.