If the abalone is sublegal and must be replaced, it will probably die. The best practice is to pick only legal size abalone. Since some abalone cannot be measured before picking, abalone irons are regulated to minimize the chance of cutting the abalone's foot. The iron must not have sharp edges and it must be smooth. Also, it cannot have any bends of a radius less than 18 inches.
Knives are illegal tools for the harvesting of abalone.
People harvesting abalone are also required to carry a U-shaped measuring device with fixed arms. Thus many abalone can be measured before picking. All sublegal abalone must be immediately returned to their original location, and efforts should be made to ensure the abalone is firmly reattached since predators will quickly attack an abalone which loses its grip.