If the splitting wedge is locked down, and can not move, and the splitting wedge is tapered equally to a point on the horizontal plane, when you split wood, the cut actually starts high, and the wedge effect of the blade, will force the wood to bind between the splitting blade and the rail. If the cutting edge were like a chisel edge, on the bottom of the splitter blade, the wood would just slide through the same space from the bottom of the blade to the rail. If the 4 way splitting wedge is a floating wedge, then it can ride up a bit and allow the wood to pass through.