This article explains how to use CoLab's cutting plane feature.
​
Cutting plane tools enable you to cut and section the model along the X, Y, and Z planes. You can toggle these cutting planes on and off as needed.

Here's an overview of each cutting option and what it does:

Resets all sections that you have made on the model, and removes all cutting planes. This resets the model back to its ‘home’ view.

To make custom cutting plane, select a face on the model and click Cutting plane on selected face.

To make a cut in the X plane, click the Cutting Plane X tool and make your cut once the plane appears.

To make a cut in the Y plane, click the Cutting Plane Y tool and make your cut once the plane appears.

To make a cut in the Z plane, click the Cutting Plane Z tool and make your cut once the plane appears.

Toggles the visibility of the cutting planes from the viewer, while keeping the sections that you made on the model.

Click ‘Reverse’ on Cutting Plane X, Y or Z to toggle the direction of that cutting plane.

In addition to clicking ‘Cutting Plane Reset’ to remove all cutting planes and reset the viewer, you can also reset the model by right clicking on any part on the model and selecting ‘Reset viewer’.

Click ‘Settings’ on the 3D model toolbar, under ‘Colour’ on the ‘General’ tab, select a colour from the ‘Capping Face Colour’ and ‘Capping Line Colour’ drop down menus.