How would constant-mesh gears be checked on the shaft?

Constant-mesh gears can be checked on the shaft by inspecting the gear teeth for wear, damage, or misalignment. This can involve visual inspection, as well as measuring the backlash between the gears to ensure proper engagement. Additionally, the shaft can be rotated to observe the smoothness of operation and listen for any unusual noises that might indicate issues. Finally, checking for proper lubrication and any signs of overheating is also essential for assessing their condition.