To use walnuts for miniature cradles, boxes and Christmas ornaments they must be carefully split in half along the seam line of the nut. Most English walnuts placed correctly in a two armed nutcracker and given gentle and even pressure will crack evenly in two along the seam. There are always some which are the wrong size or shape to work with the nutcracker, so be prepared for some splitting failures.
Placing the Walnut In the Nutcracker - Fit the walnut carefully between the arms of the nutcracker so that the pointed end of the nut is facing the top of the nutcracker and the seam line is centered on the flat edges of the nutcracker arms. If the nut fits into the nutcracker so that the arms of the nutcracker start to apply pressure at the widest part of the nut, you will likely succeed in cracking the nut evenly in half. If the arms of the nutcracker are too far forward of the nuts widest section you will have to take care to gently cradle the nut with one hand so that it doesn't move as you apply pressure with the nutcracker to make the seam open.
With the nut properly lined up in the nutcracker, gently squeeze the arms of the nutcracker until you hear the nut begin to crack. Stop and check to see where the seam is cracking.