miauu's Work Plane is a script for Autodesk 3ds Max that generates a work plane aligned to the two major axes closest to the screen axis. In its default mode the plane adjusts to the screen rotation, so turning the Perspective viewport snaps it to the dominant XY, XZ or YZ plane.
The plane can also be locked and used as a construction plane. Several methods exist for manually setting it to a specific center and axis: you can lock it to a chosen major axis and position, or snap it to selected geometry or to the polygons directly under the mouse. You can also force a manual alignment through the Work Plane commands.
Those commands sit in the Work Plane menu on the main menu bar, and you can assign hotkeys to most of them through Customize - Customize User Interface under the "miauu's Work Plane" category. As a modeling assistant it supports doing most modeling in a single perspective viewport, leaving more screen space for the model and tools, and gives a fast way to create construction planes and constrain tools to specific axes.