Fish tailing of margins in stab wound is seen with?

Fish tailing of margins in stab wound is seen with single edged knife. A knife blade with a double edge will normally produce a symmetrical elliptical wound with both ends pointed; a knife with a single-edged blade may show relative blunting ("fish-tailing") of one end of the entry slit. However, a single edged blade can produce a wound with two pointed ends, mimicking an injury from a double edged blade. A bayonet, which has a ridge along the back of the blade with a groove along each side, may produce a slit like an elongated letter "T".