# Working with Packets

## Chapter 2. Working with Packets

## The Packet Tree

A single Regina data file can store a rich variety of objects, from 3-manifold triangulations and normal surfaces to Python scripts, PDF documents and text notes. All of these objects are called packets, and are arranged in a tree-like structure as you can see below.

To view or edit a packet, just click on the packet in the tree (on some platforms, such as MacOS, you need to double-click instead). The packet will open up in a new window, as shown below.

### Uneditable Packets

Sometimes you will find that Regina does not let you make changes to a packet. This typically means that the packet is constrained by its children.

For example, if a triangulation has normal surfaces or angle structures that refer to it, then Regina will not let you change the triangulation because this would invalidate the normal coordinates and/or angle structure coordinates.

Uneditable packets such as this will be marked with a padlock in the packet viewer:

If you find yourself in such a situation, you can always clone the packet. This will create a new copy of the packet without any children, and you will be able to edit your clone instead.