diff --git a/doc/Custom-layouts.md b/doc/Custom-layouts.md
index 91e89b8..0e0dd30 100644
--- a/doc/Custom-layouts.md
+++ b/doc/Custom-layouts.md
@@ -106,15 +106,23 @@ In a layout, a key value can also start with the `loc` prefix. These are place-h
## Modmap
The ``...`` pair encloses custom mappings for modifier keys. The modmap is placed inside the ``...`` pair, but outside any row. A layout can have at most one modmap.
-A modmap can contain the following tags, each of which must have an `a` and a `b` property:
-* `` If the Shift modifier is on, the key `before` is changed into `after`.
-* `` If the Fn modifier is on, the key `before` is changed into `after`.
-
+A `` can contain any number of elements of the form:
+```xml
+
+```
+This means that when the Shift modifier is on, the key `before` is changed into `after`.
Valid values for `before` and `after` are listed in [Possible key values](Possible-key-values.md).
-There can be as many of these tags inside `` as needed.
+The supported modmaps are: ``, `` and ``.
-The clockwise circle and the round-trip gestures are affected by both Shift and Fn modmaps. The Shift mappings are used first and if that did not modify the key, the Fn mappings are used instead.
+The `` modmap is special in that the built-in Ctrl modifier will then be applied to `after`.
+For example, this will map Ctrl+в to Ctrl+V (not to v):
+
+```xml
+
+```
+
+The clockwise circle and the round-trip gestures are affected by both `` and `` modmaps. The Shift mappings are used first and if that did not modify the key, the Fn mappings are used instead.
### Example
Turkish keyboards use the Latin alphabet, but when "i" is shifted, it should produce "İ". This is achieved with the following modmap: