Connecting Rods and Caps
Connecting rods and their respective caps are used in combustion engines to convert linear motion into rotary motion. They transmit the force from the compression on top of the pistons to the crankshaft. They are sometimes constructed together with a process of breaking the cap away from the rod in the factory and must remain a matched set. These caps are matched with their corresponding connecting rods so it's important to keep the caps in order during disassembly. No matter how they are made keep the caps with their rods and you can't loose. That's why they are marked with the cylinders corresponding number, but only when necessary because they may be stamped by the manufacturer.
Marking the caps with their corresponding rods is done only when necessary. Marking an indentation on a connecting rods shaft is a bad idea. These rods are made of strong metals and often hardened to retain their strength as the engine wears. Even scratching into one of these rods will weaken it and could end in catastrophe. Most of us have seen a thrown rod usually protruding out of someone's engine block. So only mark them if you have to, the base is a good spot. Screw the nuts onto the bolts to keep the two parts together.
