# No example in the manual

**URL:** <https://gromacs.bioexcel.eu/t/no-example-in-the-manual/494>\
**Category:** User discussions\
**Created:** [July 15, 2020, 2:10am UTC](https://gromacs.bioexcel.eu/t/no-example-in-the-manual/494 "2020-07-15T02:10:51Z")\
**Posts on this page:** 1\
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**Author:** ![kevinboyd](https://avatars.discourse-cdn.com/v4/letter/k/c77e96/32.png) [@kevinboyd](https://gromacs.bioexcel.eu/u/kevinboyd)\
**Post date:** [July 18, 2020, 11:15pm UTC](https://gromacs.bioexcel.eu/t/no-example-in-the-manual/494/2 "2020-07-18T23:15:59Z")

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Hi - if you have a request, please file an issue here: [https://gitlab.com/gromacs](https://gitlab.com/gromacs)

The functional form is described here:  
[http://manual.gromacs.org/current/reference-manual/functions/restraints.html?highlight=cylinder#flat-bottomed-position-restraints](http://manual.gromacs.org/current/reference-manual/functions/restraints.html?highlight=cylinder#flat-bottomed-position-restraints)

Cylindrical restraints are under flat-bottom potentials, the restraint format is described here and contains the inputs for radius and force constant:  
[http://manual.gromacs.org/current/reference-manual/topologies/topology-file-formats.html](http://manual.gromacs.org/current/reference-manual/topologies/topology-file-formats.html)

The restraints have infinite length along the specified axis. If you really want to constrain a finite-length cylinder, you could add a few flat-bottom layer restraints along that axis.

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