If you're not squeamish, the lobsters can also be killed by inserting the point of a sharp knife through the cross mark on their backs.
Kill lobsters by plunging them headfirst into salted boiling water and cooking for 1 minute. Remove, and drain.
Place lobsters on a medium-hot grill. Cook for 8 to 10 minutes, turning occasionally to avoid burning the shells.
Crack a claw to see if it is fully cooked (the meat should be opaque). If not, detach claws, and return to grill for a few minutes more. Using kitchen scissors, split lobsters lengthwise by cutting along underside of tail, leaving back of shell intact. Scrape out red coral, if any, and green tomalley, and combine with melted butter for a dipping sauce, if desired. Keep lobsters warm on a platter covered with foil until ready to serve. Garnish with lemon wedges and serve with melted butter, if desired.