5. Align: To adjust specified variable elements of an item to bring about optimum or desired
6. Calibrate: To determine and cause corrections to be made or to be adjusted on instruments of test,
measuring, and diagnostic equipment used in precision measurement. Consists of comparisons of
two instruments, one of which is a certified standard of known accuracy, to detect and adjust any
discrepancy in the accuracy of the instrument being compared.
7. Remove/Install: To remove and install the same item when required to perform service or other
maintenance functions. Install may be the act of emplacing, seating, or fixing into position a spare,
repair part, or module (component or assembly) in a manner to allow the proper functioning of an
equipment or system.
8. Replace: To remove an unserviceable item and install a serviceable counterpart in its place.
"Replace" is authorized by the MAC and assigned maintenance level is shown as the third position
code of the Source, Maintenance and Recoverability (SMR) code.
9. Repair: The application of maintenance services, including fault location/troubleshooting,
removal/installation, disassembly/assembly procedures, and maintenance actions to identify troubles
and restore serviceability to an item by correcting specific damage, fault, malfunction, or failure in a
part, subassembly, module (component or assembly), end item, or system.
The following definitions are applicable to the "REPAIR" maintenance functions of
Service, Inspect, Test, Adjust, Align, Calibrate, and/or Replace:
Fault location/troubleshooting The process of investigating and detecting the cause
of equipment malfunctioning; the act of isolating a fault within a system or Unit Under
Disassembly/Assembly The step-by-step breakdown (taking apart) of a
spare/functional group coded item to the level of its least component, that is assigned
an SMR code for the level of maintenance under consideration (i.e., identified as
Actions Welding, grinding, riveting, straightening, facing, machining, and/or
10. Overhaul: That maintenance effort (service/action) prescribed to restore an item to a completely
serviceable/operational condition as required by maintenance standards in appropriate technical
publications. Overhaul is normally the highest degree of maintenance performed by the Army.
Overhaul does not normally return an item to like new condition.
11. Rebuild: Consists of those services/actions necessary for the restoration of unserviceable equipment
to a like new condition in accordance with original manufacturing standards. Rebuild is the highest
degree of materiel maintenance applied to Army equipment. The rebuild operation includes the act of
returning to zero those age measurements (e.g., hours/miles) considered in classifying Army
Explanation of Columns in the MAC
Column (1) Group Number. Column (1) lists Functional Group Code (FGC) numbers, the purpose of
which is to identify maintenance significant components, assemblies, subassemblies, and modules with
the Next Higher Assembly (NHA).