M - Mechanical includes everything with linkages which activate or deactivate control devices. A pawl system, foot brakes and clutches, rotating gears, drive chain, sprockets and limit devices are a few examples of M.
E - Electrical connections, wiring, fuses, batteries, sensors, load moment indicators, alarms, contacts and switches all fall into the E group.
S - Structural components like boom sections, outrigger beams and jibs/extensions all qualify for the S family.
H - Hydraulic pistons, hoses, fluid reservoir, filters and seals are in the H category, along with pneumatic items such as air lines and tanks.
Though not a comprehensive list, the above MESH collection can help spot problems and determine if a more in-depth evaluation is necessary, by a qualified person.
Happy trails to my crane and rigging friends,
ITI - Field Services