When using Content Builder, you assign a layer key to the part family to allow for automatic layer mapping of part sizes. Only those layer keys predefined in the layer key style selected for your current drawing are available for selection in Content Builder. Therefore, before using Content Builder, you must select a layer standard and layer key style to use for your part sizes. Recommended selections are the MEP - AIA layer standard (AecbLayerStd4.dwg) and Mech - AIA 256-color layer key style, which are provided with AutoCAD MEP 2022 toolset. They include layer keys for all AEC objects.
A layer key style is used to map an AEC object, such as an MvPart, to a defined layer based on a layer standard. When you add an AEC object to a drawing that has a specified layer standard and layer key style, the AEC object is placed on the layer to which it is mapped. This is referred to as layer keying. For example, according to the MEP - AIA layer standard (AecbLayerStd4.dwg) and associated (Mech - AIA) layer key style, the Air Handling Unit layer key is mapped to the M-HVAC-Eqpm layer. Therefore, when you add an air handling unit to your drawing, it is assigned to the M-HVAC-Eqpm layer. For layer keying to work, you must select a layer standard and layer key style for your drawing.
To select a layer standard and layer key style
The Drawing Setup dialog box is displayed.
It is recommended that you select the AecbLayerStd4.dwg layer standard located in the folder \ProgramData\Autodesk\MEP <version>\enu\Layers to use the standard AutoCAD MEP 2022 toolset layers.
It is recommended that you select the Mech - AIA 256-color layer key style to make all AEC object layer keys available in Content Builder.