This is a technique that you can use if you bought your fivefingers tight and want them to fit like a surgical glove, or if you want them to break in faster. Do it at your own risk. It´s very simple:
1) Place your toaster on the floor and open the window (to ventilate smell)
2) Put on your fivefingers, and turn on the toaster to maximum effect (don´t put bread in
3) With your fivefingers on, place your foot just above the bread-slits in the toaster, and heat up the forefoot part until you feel the heat through the sole.
4) Immediately place the hot shoe on the floor, put all your weight on it, and push the toes into the ground while lifting your heel. This will cause the rubber in the sole to stretch under your forefoot and around the toes. Hold this position for a while, and walk around a bit while the shoe is cooling down.
5) Wait until the shoe has cooled down to evaluate the fit. Repeat if necessary.
It´s better to repeat the process a couple of times rather than heating the sole too much as this can cause the glue in the shoe to melt. You can of course also use it on other parts of the shoe that you want to break in, or change the position to tailor it to your stride and running form.