This is accomplished by manual shimming of individual shims, or automatic shimming procedure. Active shimming uses coils with adjustable current. Passive shimming involves pieces of steel with good magnetic qualities. After final adjustment of the shimming, a very reliable and high load capability bearing results. They are called thunking and shimming. Higher security padlocks typically use techniques that make shimming impossible. One method, as described before, is to use shimming coils. There are two types of shimming&colon; active and passive.