Final answer:
To differentiate steaks while cooking on the grill, wooden skewers should be inserted into 6 oz & 8 oz Filets.
Step-by-step explanation:
The steaks that should have a wooden skewer inserted in them to help differentiate while cooking on the grill are the 6 oz & 8 oz Filets. This is because filet mignons are generally thicker steaks compared to sirloins or flat irons. By inserting a wooden skewer into the center of the filets, you can easily differentiate them from other steaks while cooking.