diff --git a/doc/RTD/source/VELOCIraptorInterface/index.rst b/doc/RTD/source/VELOCIraptorInterface/index.rst
new file mode 100644
index 0000000000000000000000000000000000000000..e2582107eefed09b6bfd94d6cf208197d2e82e0f
--- /dev/null
+++ b/doc/RTD/source/VELOCIraptorInterface/index.rst
@@ -0,0 +1,176 @@
+.. VELOCIraptor Interface
+ Folkert Nobels, 8th October 2018
+
+VELOCIraptor Interface
+======================
+
+In SWIFT it is possible to run a cosmological simulation and at the same time
+do on the fly halo finding at specific predefined intervals. Because of this
+we will explain on this page how we can set up an simulation using VELOCIraptor
+(formerly STructure Finder). After this we will explain what the outputs of
+VELOCIraptor will be.
+
+Configuring SWIFT
+-----------------
+
+In the following three paragraphs we will explain how to setup VELOCIraptor,
+how to compile it and how to compile SWIFT with VELOCIraptor.
+
+
+Setting up VELOCIraptor
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Before we can run SWIFT with VELOCIraptor we first need to download
+VELOCIraptor. This can be done by cloning the repository on GitHub_::
+
+ git clone https://github.com/pelahi/VELOCIraptor-STF
+
+Currently the best version that works with SWIFT is the swift-interface branch
+of VELOCIraptor, to get this branch use::
+
+ cd VELOCIraptor-STF git fetch git checkout swift-interface
+
+To get the default that works with SWIFT simply copy the SWIFT template file in
+the ``Makefile.config``::
+
+ cd stf cp Makefile.config.SWIFT-template Makefile.config
+
+Depending on your compiler you want to change the first 20 lines of your
+``Makefile.config`` to work with your compiler and whether you want to use MPI
+or not.
+
+
+Compiling VELOCIraptor
+~~~~~~~~~~~~~~~~~~~~~~
+
+After we downloaded the files and made a configuration file we can compile
+VELOCIraptor as follows::
+
+ make lib make libstf
+
+After the compilation of your code, there is an additional folder created in
+the ``VELOCIraptor-stf/stf`` directory called ``lib`` this directory has the
+libary of VELOCIraptor and is required to run SWIFT with
+VELOCIraptor. Note that VELOCIraptor needs a serial version of the
+HDF5 library, not a parallel build.
+
+Compiling SWIFT
+~~~~~~~~~~~~~~~
+The next part is compiling SWIFT with VELOCIraptor and assumes you already
+downloaded SWIFT from the GitLab_, this can be done by running::
+
+ ./autogen.sh ./configure
+ --with-velociraptor=/path/to/VELOCIraptor-STF/stf/lib make
+
+In which ``./autogen.sh`` only needs to be run once after the code is cloned
+from the GitLab_, and ``/path/to/`` is the path to the ``VELOCIraptor-STF``
+directory on your machine. In general ``./configure`` can be run with other
+options as desired. After this we can run SWIFT with VELOCIraptor, but for this
+we first need to add several lines to the yaml file of our simulation::
+
+
+ #structure finding options
+ StructureFinding:
+ config_file_name: stf_input_6dfof_dmonly_sub.cfg
+ basename: ./stf
+ output_time_format: 1
+ scale_factor_first: 0.02
+ delta_time: 1.02
+
+In which we specify the ``.cfg`` file that is used by VELOCIraptor. In the case
+of the Small Cosmological Volume DMO example we can run a simulation with halo
+finder as::
+
+ cd examples/SmallCosmoVolume_DM
+ ../swift -c -s -G -x -t 8 small_cosmo_volume_dm.yml
+
+In which there is an additional ``-x`` option which activates the VELOCIraptor
+interface.
+
+
+VELOCIraptor Output
+-------------------
+
+In general VELOCIraptor outputs six files per snapshot, of which 2 files are
+for unbound particles specifically. In this part we will explain what is
+inside the different files.
+
+Catalog_groups file
+~~~~~~~~~~~~~~~~~~~
+
+The first file that is output by VELOCIraptor is the ``.catalog_group`` file,
+this file contains all the information that is group specific, the interesting
+data in the ``.catalog_group`` files are:
+
++ The ``group_size``: gives a list of all the halos and the number of particles
+ in the halo, this list is numbered from 0 until the number of groups minus
+ one.
++ The ``Num_of_groups`` or ``Total_num_of_groups``: gives the total number of
+ groups in the snapshot.
++ The ``Offset`` list: This list gives the offset off the particles. In the
+ output of VELOCIraptor there is no file which has an ID for every particle
+ and a corresponding group, rather the particles are ordered according to in
+ which group they are. So if we want to access the particles in group 0, we
+ need to look at the particles from ``Offset[0]`` until ``Offset[1]`` in the
+ ``.catalog_particles`` hdf5 file. In general this means that for group N we
+ need to look at particles ``Offset[N]`` until ``Offset[N+1]``.
++ The ``Offset_unbound`` list: This list works exactly the same as the
+ ``Offset`` list only this list is for the gravitational unbound particles.
+
+Catalog_particles file
+~~~~~~~~~~~~~~~~~~~~~~
+
+The second file that is produced by VELOCIraptor is the ``.catalog_particles``
+file, this file contains mainly all the IDs of the particles and mainly has two
+interesting things:
+
++ The ``Num_of_particles_in_groups`` and ``Num_of_particles_in_groups``
+ parameter: Gives the total number of particles in the file or which are found
+ in the halo.
++ The ``Particle_IDs``: The list of particles as sorted by halo, in which halo
+ the individual particles are present can be found by using the
+ ``.catalog_group`` file and the corresponding ``Offset`` list.
+
+Besides the ``.catalog_particles`` file, there is also a
+``.catalog_particles.unbound`` file, this file contains the same information
+but only for the unbound particles, a particle can only be present in one of
+these two lists.
+
+Catalog_parttypes file
+~~~~~~~~~~~~~~~~~~~~~~
+
+The third file that is produced by VELOCIraptor is the ``.catalog_parttypes``
+file, this file contains the information what type of particle every particle
+is, ordered the same as in ``Particle_IDs`` in ``.catalog_particles``. There
+are only two interesting parameters of the file which are:
+
++ The ``Num_of_particles_in_groups`` parameter: Gives the total number of
+ particles in the file which are in a halo.
++ The ``Particle_types`` list: Gives a list of particles types similar to the
+ snap shots (0 - gas, 1 - dm, 4 - stars).
+
+Besides the ``.catalog_parttypes`` file, there is also a
+``.catalog_parttypes.unbound`` file, this file contains this information for
+the unbound particles.
+
+Properties file
+~~~~~~~~~~~~~~~
+
+The Fourth file is the ``.properties`` file, this file contains mainly physical
+useful information of the corresponding halos. Some usefull physical parameters
+are:
+
++ ``Mass_200crit``: The mass of a halo with an overdensity on average of
+ :math:`\Delta=200` based on the critical density of the Universe.
++ ``Mass_200mean``: The mass of a halo with an overdensity on average of
+ :math:`\Delta=200` based on the mean density of the Universe.
++ ``Mass_FOF``: The friends-of-friends mass of the halos.
++ ``Mvir``: The viral mass of the halos.
++ ``Other parameters``: Soon
+
+
+
+
+.. _GitHub: https://github.com/pelahi/VELOCIraptor-STF
+.. _GitLab: https://gitlab.cosma.dur.ac.uk/swift/swiftsim
+
diff --git a/doc/RTD/source/index.rst b/doc/RTD/source/index.rst
index 05c15c5a081cb03ae4e53c26bf6fe4e8dd78dfd5..21eb7253c62c09595dd547540d9923c1be866e6a 100644
--- a/doc/RTD/source/index.rst
+++ b/doc/RTD/source/index.rst
@@ -21,3 +21,4 @@ difference is the parameter file that will need to be adapted for SWIFT.
EquationOfState/index
NewOption/index
Task/index
+ VELOCIraptorInterface/index