Final answer:
Malleable iron threaded fittings are usually manufactured with right-handed threads, following the rule for easy compatibility in plumbing systems.
Step-by-step explanation:
When manufactured, malleable iron threaded fittings are normally supplied with right-handed threads. This is the standard threading direction used for most plumbing applications because it follows the conventional 'righty-tighty, lefty-loosey' rule.
Right-handed threads means that the fittings will tighten or screw in clockwise and loosen or unscrew counter clockwise. The use of right-handed threads in malleable iron threaded fittings enables compatibility with other components and tools in plumbing systems.