Preparations

A useful kerning pass starts with a class system and repeatable text. Classes reduce repeated decisions; well-chosen strings expose the cases where those shared decisions need exceptions.

Building Kerning Classes

Open Window > Panels > Classes and choose the kerning class type. A left class occupies the left position of a visual pair, so its members are grouped by their right-side profile. A right class occupies the right position and is grouped by its members' left-side profile.

A both-sided class can serve in either position. Use it only when the membership makes sense on both sides. Similar left profiles do not imply similar right profiles.

Create and check a class

1. Select the glyphs that should share one side's behavior.
2. In the Classes panel, add a left, right, or both-sided kerning class.
3. Add the selected glyphs and give the class a clear name.
4. Inspect its members against representative glyphs on the opposite side.
5. Move outliers to another class or plan an appropriately scoped exception.

Prefixes such as L_ and R_ make position-in-pair names easy to distinguish: L_A and R_A are different classes. They are an organizational convention, not mandatory syntax that makes the shapes kern alike.

A glyph can belong to one kerning class on each side. When a proposed assignment conflicts with an existing same-side class, review whether to move the glyph, retain its old membership, or cancel. Membership changes can affect many pairs, even if no pair values are edited at that moment.

Use the panel's Preview, Table, and List views to check shapes, names, and membership. Do not merge classes merely because their representatives look similar. Include accents, swashes, alternates, and the actual script context in the comparison.

The Classes panel shows the selected class alongside glyph previews and membership data, helping you compare names with shapes.

Other assignment controls

The Set Kerning Class dialogs provide a quicker route for assigning the current glyph or selection. They are available from the Glyph panel, Font-window status controls, and Font > Kerning > Set Left Kerning Class or Set Right Kerning Class. Choose an existing class or deliberately create a new one, then inspect the resulting membership.

The contextual widget's Glyph state also exposes left and right class fields. Check their labels rather than relying only on their screen positions. Preferences > Spacing > Edit kerning classes by position in pair determines whether these fields are arranged by pair position or by the side of the displayed glyph they describe. In the latter arrangement, the right-class field appears beside the glyph's left side.

Use Font > Kerning > Generate Kerning Classes, or Generate Kerning Classes in the Classes panel menu, to propose groups from the drawings. Treat the result as a starting point: review script separation, accents, and distinctions the outline analysis cannot decide semantically. An automatically proposed class is not evidence that every member accepts the same values in all contexts.

These classes drive FontLab's visual kerning. OpenType @-classes used for writing substitution rules are a different category, even though the Classes panel manages both. Kerning classes are master-related; substitution-authoring classes are shared font-level lists.

Preparing Kerning Strings

Keep test material that reflects the glyphs and classes in this font. A list for another typeface may omit your alternates or repeatedly test combinations that do not exist in your design.

Save window texts

Enter a useful string in the Glyph window and use the sidebar's Save current text control to retain it. Preferences > Texts provides another place to maintain reusable text. Keep the spacing test strings from Spacing Glyphs separate from strings for common kerning pairs and troublesome exceptions.

Use real words as well as neutral surrounding letters. A pair that looks balanced in isolation can interrupt the rhythm of a word; a word can also hide which pair is responsible for the problem.

Automatic pair-context text follows each side’s case and small-cap suffix independently. A lowercase glyph on one side does not become a small cap merely because its partner is one. Inspect the generated context against the actual glyph names in the font.

Use Pairs & Phrases

Open Window > Panels > Pairs & Phrases. Pairs mode supplies marked pair examples; Texts mode supplies running text. Auto mode chooses according to the current editing mode. Selecting an entry loads it into the Glyph window, and selecting several entries lets you work through a larger set.

The Texts list keeps reusable words and spacing strings together. The mode selector is at the lower left.

The supplied lists include Latin, Latin Extended, and Cyrillic material. The Latin and Cyrillic lists rank useful pair contexts; the extended Latin material adds neutral contexts around the target pair. They provide substantial starting coverage, not a completeness guarantee for your character set.

Use Edit Pairs & Phrases to create a named custom list, edit its content, or import a plain-text file. Keep the list's name descriptive enough to distinguish, for example, capital-diagonal pairs from small-cap punctuation.

The pair-list editor keeps named collections on the left and their test text on the right.

Two supported formats make the target pair explicit. A glyph-name pair list can begin:

#KPL:P: Capitals
T A
T adieresis

A word-context list can begin:

#KPL:W: Words
T ypography
auf arbeiten

In the second form, the space marks the pair boundary in the phrase; it is not simply an ordinary space to add to the proof word. These KPL formats support MetricsMachine-style exchange. Check imported entries against the font's actual glyph names and character coverage.

The Superkerning panel keeps its own suggested-pair list, independent of Pairs & Phrases. Choosing a list there does not replace the collection you are using here.

Arrange a pass around the class system: first representative class pairs, then less typical members, then exceptions and running text. Save newly discovered problem strings so that the next master or revision can be checked against the same evidence.