A string bet is an illegal action in serious casinos and tournaments where the player does not place the total chips at once, making multiple movements toward the pot while observing the opponent’s reaction. The rule against string bets exists to prevent players from gaining valuable information through physical reactions before committing the full bet. In live casinos, string bets are voided and the player must complete only the portion placed in the first movement. The only exception is verbally declaring the full bet amount before placing chips.