Index: src/sas/sasgui/perspectives/fitting/media/fitting_help.rst
===================================================================
--- src/sas/sasgui/perspectives/fitting/media/fitting_help.rst	(revision a7c6f38e460b03102c3235b21c334a55fd344082)
+++ src/sas/sasgui/perspectives/fitting/media/fitting_help.rst	(revision 84ac3f1346f94e3781ba42c6405173781c110161)
@@ -432,14 +432,14 @@
 Change the default values of the model parameters by hand until the theory line
 starts to represent the experimental data. Then check the tick boxes alongside
-the 'background' and the 'scale' parameters. Click the *Fit* button. SasView
+the 'background' and 'scale' parameters. Click the *Fit* button. SasView
 will optimise the values of the 'background' and 'scale' and also display the
 corresponding uncertainties on the optimised values.
 
 .. note::
-   If a parameter uncertainty is unrealistically large, or if it displays as
-   NaN either the model is a poor representation of the data, the parameter in
-   question is either highly correlated with one or more other fitted parameters
-   or at least that the model is relatively insensitive to the value of that
-   particular parameter.
+   If the uncertainty on a fitted parameter is unrealistically large, or if it
+   displays as NaN, the model is most likely a poor representation of the data,
+   the parameter in question is highly correlated with one or more of the other
+   fitted parameters, or the model is relatively insensitive to the value of
+   that particular parameter.
 
 In the bottom left corner of the *Fit Page* is a box displaying the normalised
@@ -447,8 +447,8 @@
 
 Now check the box for another model parameter and click *Fit* again. Repeat this
-process until most or all parameters are checked and have been optimised. As the
-fit of the theory to the experimental data improves, the value of 'Reduced Chi2'
-will decrease. A good model fit should produce values of Reduced Chi2 close
-close to one, and certainly <100. See :ref:`Assessing_Fit_Quality`.
+process until all relevant parameters are checked and have been optimised. As
+the fit of the theory to the experimental data improves, the value of 'Reduced
+Chi2' will decrease. A good model fit should produce values of Reduced Chi2
+close to one, and certainly << 100. See :ref:`Assessing_Fit_Quality`.
 
 SasView has a number of different optimisers (see the section :ref:`Fitting_Options`).
@@ -465,7 +465,11 @@
 *the Data Explorer is checked (see the section* :ref:`Loading_data` *).*
 
-This mode is an extension of the :ref:`Single_Fit_Mode` that fits two or more data
-sets *to the same model* simultaneously. If necessary it is possible to constrain
-fit parameters between data sets (eg, to fix a background level, or radius, etc).
+This mode is an extension of the :ref:`Single_Fit_Mode` that allows for some
+relatively extensive constraints between fitted parameters in a single *FitPage*
+or between several *FitPage*'s (eg, to constrain all fitted parameters to be the
+same in a contrast series of *FitPages* except for the solvent sld parameter,
+contrain the length to be twice that of the radius in a single *FitPage*,
+fix the radius of the sphere in one *FitPage* to be the same as the radius of
+the cylinder in a second *FitPage*, etc).
 
 If the data to be fit are in multiple files, load each file, then select each file
@@ -504,11 +508,25 @@
 next to *Add Constraint?* in the *Fit Constraints* box.
 
+To constrain all identically named parameters to fit *simultaneously* to the
+same value across all the *Fitpages* use the *Easy Setup* drop-down buttons in
+the *Const & Simul Fit* page.
+
 *NB: You can only constrain parameters that are set to refine.*
+
+Constraints will generally be of the form
+
+  Mi Parameter1 = Mj.Parameter1
+
+however the text box after the '=' sign can be used to adjust this
+relationship; for example
+
+  Mi Parameter1 = scalar \* Mj.Parameter1
+
+A 'free-form' constraint box is also provided.
+
+Many constraints can be entered for a single fit.
 
 When ready, click the *Fit* button on the *Const & Simul Fit* page, NOT the *Fit*
 button on the individual *FitPage*'s.
-
-Simultaneous Fits without Constraints
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 The results of the model-fitting will be returned to each of the individual
@@ -518,35 +536,8 @@
 each fit. To see the Reduced Chi2 value for a specific *FitPage*, click the 
 *Compute* button at the bottom of that *FitPage* to recalculate. Note that in
-doing so the degrees of freedome will be set to Npts.
-See :ref:`Assessing_Fit_Quality`.
-
-Simultaneous Fits with Constraints
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Use the *Easy Setup* drop-down buttons in the *Const & Simul Fit* page to set
-up constraints between *FitPage*'s.
-
-Constraints will generally be of the form
-
-  Mi Parameter1 = Mj.Parameter1
-
-however the text box after the '=' sign can be used to adjust this
-relationship; for example
-
-  Mi Parameter1 = scalar \* Mj.Parameter1
-
-A 'free-form' constraint box is also provided.
-
-Many constraints can be entered for a single fit.
-
-The results of the model-fitting will be returned to each of the individual
-*FitPage*'s.
-
-Note that the Reduced Chi2 value returned is the SUM of the Reduced Chi2 of
-each fit. To see the Reduced Chi2 value for a specific *FitPage*, click the 
-*Compute* button at the bottom of that *FitPage* to recalculate. Note that in
-doing so the degrees of freedome will be set to Npts.
+doing so the degrees of freedom will be set to Npts.
 See :ref:`Assessing_Fit_Quality`.  Moreover in the case of constraints the
-degrees of freedom are less than one might think do to those constraints.
+degrees of freedom are less than one might think due to those constraints.
+
 .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
 
@@ -773,4 +764,7 @@
 .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
 
-.. note::  This help document was last changed by Paul Butler, 10 September
-   2017
+.*Document History*
+
+| 2017-09-10 Paul Butler
+| 2017-09-15 Steve King
+| 2018-03-05 Paul Butler
Index: src/sas/sasgui/perspectives/fitting/media/residuals_help.rst
===================================================================
--- src/sas/sasgui/perspectives/fitting/media/residuals_help.rst	(revision a7c6f38e460b03102c3235b21c334a55fd344082)
+++ src/sas/sasgui/perspectives/fitting/media/residuals_help.rst	(revision 84ac3f1346f94e3781ba42c6405173781c110161)
@@ -34,12 +34,12 @@
   =  \sum[(Y_i - \mathrm{theory}_i)^2 / \mathrm{error}_i^2]
 
-Fitting typically minimizes the value of $\chi^2$.  However, for assessing the
-quality of the model and its "fit" this parameter is not terribly helpful on its
-own.  Thus *SasView* instead displays a normalized version of this parameter,
-using the traditional reduced $\chi^2_R$.  This is the $\chi^2$ divided by the
-degrees of freedom (or DOF). The DOF is simply the number of data points being
-considered reduced by the number of free (i.e. fitted) parameters. Note that
-model parameters that are kept fixed do *not* contribute to the DOF (they are
-not"free". This reduced value is then given as
+Fitting typically minimizes the value of $\chi^2$.  For assessing the quality of
+the model and its "fit" however, *SasView* displays the traditional reduced
+$\chi^2_R$ which normalizes this parameter by dividing it by the number of
+degrees of freedom (or DOF). The DOF is the number of data points being
+considered, $N_\mathrm{pts}$, reduced by the number of free (i.e. fitted)
+parameters, $N_\mathrm{par}$. Note that model parameters that are kept fixed do
+*not* contribute to the DOF (they are not "free"). This reduced value is then
+given as
 
 .. math::
@@ -49,10 +49,9 @@
   / [N_\mathrm{pts} - N_\mathrm{par}]
 
-where $N_\mathrm{par}$ is the number of *fitted* parameters. Note that this
-means the displayed value will vary depending on the number of parameters used
-in the fit.  In particular, when doing a calculation without a fit (e.g.
-manually changing a parameter) the DOF will now equal $N_\mathrm{pts}$ and the
-$\chi^2_R$ will be the smallest possible for that combination of model, data
-set and set of parameter values.
+Note that this means the displayed value will vary depending on the number of
+parameters used in the fit. In particular, when doing a calculation without a
+fit (e.g. manually changing a parameter) the DOF will now equal $N_\mathrm{pts}$
+and the $\chi^2_R$ will be the smallest possible for that combination of model,
+data set, and set of parameter values.
 
 When $N_\mathrm{pts} \gg N_\mathrm{par}$ as it should for proper fitting, the
@@ -99,2 +98,3 @@
 | 2015-06-08 Steve King
 | 2017-09-28 Paul Kienzle
+| 2018-03-04 Paul Butler
