Jack-it wasn't Jack but, it was Sam n Eric(the twins) which told Ralph.
Roger has prepared a stick sharpened at both ends for Ralph. This means that he has the same end in mind for Ralph as the sow (female pig). The sow was killed rather brutally killed prior to having her decapitated head mounted on a stick sharpened at both ends as an offering to "the Beast." This is a thinly vailed threat on Roger's part.
Samneric tells Ralph that Roger sharpened a stick at both ends. This means that when they kill him, they will put him on the stick like the pig's head.
-Spoiler warning- The only other time a stick is sharpened at both ends is after Jack killes the sow and offers the head to the beast for protection. It means that Roger wants to murder Ralph, cut his throat, and put his disembodied head on the stick as an offering to Satan.
Ralph learns from Samneric that Jack plans to have his tribe hunt him the next day and that Roger has sharpened a stick at both ends.
They warn Ralph that Jack plans to hunt him the next day and that Roger has "sharpened a stick at both ends."
The lord of the flies originally hung on a stick sharpened at both ends. One end in the earth and the other supporting the pig head. Roger intends to do this same thing to Ralph if they kill him, but replacing the pigs head with Ralphs. They dont kill Ralph :)
Jack and Roger have sharpened a stick at both ends to hunt and kill Ralph. Their plan is to hunt Ralph like they did with the sow, to terrify him and flush him out. Samneric warn Ralph that they are being hunted and that Jack's tribe will sharpen a stick at both ends and have Roger guard the way in.
Roger and Jack likely intended to use the sharpened stick as a weapon. Its design as a spear with both ends sharpened suggests they intended to hunt or harm someone or something. This weapon could have been used for hunting animals or as a tool to establish power or control over others.
Ralph, Jack and Roger search the island and climb the mountain in their search for "the beast."
Roger does not say anything to Ralph as they approach the "rock castle" in the Lord of the Flies. Instead, Roger silently throws rocks at them from above, demonstrating his cruelty and violent tendencies.
When Samneric mention that Roger sharpened a stick at both ends in "Lord of the Flies," it signifies the increasingly violent and dangerous nature of Roger. Sharpening a stick at both ends suggests a malicious intent to harm others, foreshadowing the savagery that will eventually consume the boys on the island. It also symbolizes the loss of civilization and the descent into barbarism.
*Ralph *Jack *Sam & Eric *Roger *Piggy *Simon *Percival *Bill