Why was the sick sharpened at both ends?

When Jack and his hunters killed the Sow, Jack ordered that a stick should be sharpened at both ends, so that he could stick one point in the ground and mount the sow's head on the other point, to leave it as an offering for the beast. As it turned out the ground was rocky and the stick was simply jammed into a crack. However, later in the novel, when Ralph asked Samneric what Jack planned to do to him one of the twins told him that "Roger sharpened a stick at both ends." The obvious inference was that Jack and his hunters intended to kill Ralph and mount his head on a stick as an offering to the beast.