Katana 3.5v5 docs:

MaterialAssign

Assigns materials to geometry in the scene graph.

Connection Type	Connection Name	Function
Input	input	The material in the node graph that you want to apply tot he geometry in the scene graph.

Control (UI)	Default Value	Function
CEL	N/A	Sets the CEL specification of scene graph locations on which the assignment acts. For more information, see the CEL Reference document found on the documentation HTML page (accessed through Help > Documentation) or the CEL widget parameters in Common Parameter Widgets.
materialAssign	N/A	Specifies the material to assign. Typically, you middle-mouse drag this from under /root/materials/geo in the scene graph. The materialAssign parameter options are available by clicking the dropdown menu. For more information, refer to the Path Selection Widget Types in Common Parameter Widgets.

Control (UI)

Default Value

Function

CEL

N/A

Sets the CEL specification of scene graph locations on which the assignment acts.

For more information, see the CEL Reference document found on the documentation HTML page (accessed through Help > Documentation) or the CEL widget parameters in Common Parameter Widgets.

materialAssign

N/A

Specifies the material to assign. Typically, you middle-mouse drag this from under /root/materials/geo in the scene graph. The materialAssign parameter options are available by clicking the dropdown menu.