> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ntop.com/llms.txt
> Use this file to discover all available pages before exploring further.

# How to determine a Nastran classification for an nTop block

## Objective:

To determine a force/restraint block's Nastran classification.

## Applies to:

* Nastran Simulations
* nTop Simulations

## Solution:

1. This tutorial begins with a pre-setup **Export Static** **Analysis** block that contains one **Point Force** block as the boundary condition and an **FE Model** block of an aluminum cube. To learn how to set up a simulation, please consult this [article](/help-articles/knowledge-base/structures/how-can-i-set-up-a-simulation).

![An example static analysis with one applied Point Force boundary condition.](https://files.learn.ntop.com/help-articles/structures/8753446595731.png)

2. Export the results as a Nastran file type (\*.bdf, \*.dat, \*.nas).

![Export the static analysis using the Export Static Analysis block. Save the results as a Nastran file type](https://files.learn.ntop.com/help-articles/structures/8753711927699.png)

3. Open the file using a text editing program. For this example, I will be using Notepad++.

![The static analysis results file opened in a text editing software.](https://files.learn.ntop.com/help-articles/structures/8753952804883.png)

4. Last, scroll down the document until you pass the CTETRA lines. CTETRA references a four-sided solid element connection, so all of these lines reference the solid object. Since the only force we applied was the **Point Force** block, we can see that the Nastran classification is RBE3.

![A gif showing how to find the nastran classification for the Point Force block. You scroll down in the text document until the point force information is reported. The classification in this example is RBE3.](https://files.learn.ntop.com/help-articles/structures/8754155082131.png)

And that's it! You've successfully determined a block's Nastran classification.

Are you still having issues? Contact the [support team](https://support.ntopology.com/hc/en-us/requests/new), and we'll be happy to help!

## Attachment:

* [Nastran Classification Example File](https://files.learn.ntop.com/Support%20Article%20Example%20Files/Knowledge%20Base/Simulation/Nastran%20Classification%20for%20Block%20Example.ntop)

## Keywords:

*simulation how to classification RBE3 RBE2 CTETRA Nastran*