Applying InGutter to an existing layout, you always get a left and right inset along with the rules, even if you have only inner rules. Understanding how the gutter, the inset and the global width interact is an important point as it directly regards how InGutter is implemented “under the hood.” Let's consider a basic example and study how the script behaves by default (click the screenshot to zoom in) :

InGutter always preserves the global width, while it adjusts the gutter and the left/right inset.

As you can see, when we keep the default settings and simply create inner rules, InGutter automatically inserts left and right inset around the whole text frame. Also, it does not preserve the original gutter. Instead, it preserves the total width of the frame and the individual width of the columns so that the composition and the justification of the text does not change.

The rule behind is that we must always have the final gutter equal to the total inset width (i.e. left + right inset), even if no side rules are used. This is the fundamental constraint of the script. It directly results from the way our vertical rules are built. Deeper details on the underlying trick have been exposed in our original post, “Introducing InDesign Column Rules”, which you can still refer to explore other technical aspects. In short, InGutter needs to distribute in a balanced manner a set of paragraph rules. This is done through the Vertical Justification of the additional frame and, thanks to these settings, the trick properly works with no distortion even when the group is dynamically resized by the user, as shown below:

Once a frame has been properly treated by InGutter, it can be manually resized or transformed.

However, the trick has a cost. If you run InGutter on a three-column text frame whose gutter is originally set to 8 mm, the script's dialog will first suggest to reset the gutter to 5.333 mm. Why? Because the original inner spacing (8 + 8 = 16) must now be obtained including left and right inset. Let X be the total inset spacing (i.e. left + right). InGutter's Primary Rule says that X is also the required gutter, so we must have:
    X + 2X = 16,  which leads to X = 16/3   (= 5.333).

The first time InGutter considers a text frame, it suggests to fix the gutter to get a correctly balanced inset.

Therefore, users who are in refining an existing layout may be confused. In many workflows the gutter is already set, and the visible bounds of the frame are not intended to be changed. At first sight, InGutter does not seem to allow any workaround…

Forcing the gutter, then adjusting the width

Given a text frame already prepared, of course you can run InGutter and manually change the gutter so that it matches the original value. However, since the corresponding inset spacing is automatically computed and inserted (while the total width of the frame is maintained), you will probably experience the following issue:

When we tell InGutter to use the original gutter width (8 mm) rather than the corrected value (5.333 mm), the column width is reduced in order to make room to the inset spacing (left: 4 + right:4).

In the above screenshot, the individual width of the columns is reduced and then the composition is modified, as a total inset width of 8 mm (left: 4 mm + right: 4 mm) has been inserted by the script. Note that this offset is exactly the value of the gutter that the user has just entered.

From that point, you might consider a good idea to manually remove the left and right inset spacings using the InDesign's Text Frame Options dialog… But the figure below shows why it's a bad idea:

Trying to manually fix the issue by removing the inset spacing? As a result, you get biased rules (out of centre).

Indeed, the original layout is restored but the vertical rules are now out of center of their respective gutter. This little experiment makes clear that we need an adjusted inset to ensure the balanced locations of the rules.

In fact, the workaround we are looking after is really simple: just increase the overall width of the group by a value equal to the gutter. This way you preserve both the original column width, the gutter and the existing layout:

The solution: just increase by 8 mm the overall width of the group.

Note. — This solution has one disadvantage: the geometric bounds of the final object is larger that the original frame. Although this makes no visible difference, you cannot place and move the object along the guides and margins of your prepared document. One option is to create specific guides that fit the extra space.

Step by step

Let's summarize the steps that let you add vertical rules to any text frame already laid out:

1) Select the object and run InGutter.

2) In the Gutter field (which has been automatically modified), enter the original value—say 8—of the gutter.

3) Set the rules (and other parameters) to your needs.

4) Click Update.

5) From the InDesign's Control panel, add the gutter's value (+8) to the overall width of the group. (Make sure the Reference Point is then at the center of the square.)

(I admit that such adjustment should be supported by the script itself—e.g. through an option “Adjust the overall width.”—I will consider this improvement.)

About Wrapping Issues and Anchored Objects

As in the above example, your frame may contain anchored objects (e.g. a picture or more complex graphic components). To avoid wrapping issues or unexpected repositioning, I think the best practice is to anchor the object at the very beginning of the article and to fine-tune its position via the Anchored Object Options dialog.

Start by setting the Text Wrap attributes of the object to be anchored (the Jump Object option is usually the best) and make sure that the target text frame will not ignore text wrap. Then anchor the object and apply a custom position. Use the system of reference points to specify how the object should be placed relative to the frame bounds, the column edge and/or the baseline, and check “Prevent Manual Positioning.”

The graphic frame is anchored at the beginning of the text.

In my example, the title is based on a paragraph that spans two columns (using the Span Columns feature). But InGutter has no special mechanism to address this situation. To make the title area cover and hide the vertical rule, we have to tweak the underlying paragraph style: we set up an heavy Paragraph Rule based on the [Paper] swatch. This way the title works as an opaque region:

How to hide the vertical rule behind the title area.

Of course, if you apply a background through InGutter, you will need to set the same swatch and tint for the title paragraph rule:

Changing the background.

Conclusion: with a little attention to detail you can still use InGutter in sophisticated layouts.