Any 3D body you create in Shapr3D is guaranteed to be a watertight, solid body without any holes on the surface. This type of body is called a **manifold geometry**. While you’re transforming your model, our app will prevent you from changing your manifold geometry into a non-manifold one.

## Manifold geometry

You can unfold the 3D shape into a 2D surface and the 2D shape’s normals all point in the same direction.

## Non-manifold geometry

You can unfold the 3D shape into a 2D surface and the 2D shape’s normals don’t all point in the same direction due to a shared edge or 2 faces connected at a single point.

Non-manifold geometry can also be a geometry that includes an intersecting edge without volume. Though intersecting edges can't often be seen from the outside of the model, they render the design impossible to print.

There are different types of non-manifold geometry:

- T-type

If you have 3 faces sharing a single edge, you can make this body watertight by adding volume to the third face or deleting it completely. - Bow-type

In this instance, multiple surfaces are connected at one point and don’t share an edge. Make this manifold by either disconnecting the two geometries or deleting one of them. - Open geometry

Make your model manifold by creating volume in your model: Adjust the wall thickness or add additional surfaces to your geometry.