# QOTW #1: What is the difference between the Offset Body and Thicken Body blocks?

Hello everyone and welcome to our Question of the Week series! Each week we will be going through questions that our Educational users send in. This week we are answering the question:

## What is the difference between the Offset Body and Thicken Body blocks?

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When working with parts in nTop, sometimes you may need to increase or decrease the size of the part. There are two main options for doing this: Thicken Body and Offset Body.

Thicken Body: Create a thickened hollow Implicit Body using an Implicit boundary as a mid-surface.

The Thicken Body block will thicken the part in both directions, using the boundary of the body as the centerline of the thickness. Thicken Body is best to use for 1D or 2D parts, such as CAD surfaces or graph lattices.

Offset Body: Offset the surface boundary of an Implicit Body inward or outward.

Offset Body works best for objects that already have a volume. It will adjust the surface boundary of the part. A positive value will increase the surface boundary, while a negative value will decrease it.

#### Usage in Lattices and Surfaces: Thicken Body Recommended

When an Offset Body is used for a graph lattice, the Offset occurs in every direction since the graph lattice boundary is 2D, which doubles the thickness value. Watch the gif below to see the difference between Thicken Body and Offset Body of the same thickness value on a graph lattice. The Thicken Body creates a total thickness of 1 mm for the lattice, while the Offset Body creates a total thickness of 2 mm. Negative thickness and offset values will result in no volume since a surface or graph lattice cannot decrease in volume.

#### Usage in Volumes: Offset Body Recommended

Since Thicken Body uses the boundary as a midpoint, it is recommended to use Offset Body when you are starting with a part that already has volume. In the gif below, Thicken Body only adds 0.5 mm to the outside of the body, and Offset Body moves the boundary of the body out by the full 1 mm.