diff --git a/cheatsheet.md b/cheatsheet.md
index 2df7324..e2fef67 100644
--- a/cheatsheet.md
+++ b/cheatsheet.md
@@ -8,7 +8,10 @@ June 2022. Version 0.7.0.
 
 ## Machine-Oriented Binary Syntax
 
-For a value `v`, we write `«v»` for the binary encoding of `v`.
+For a value `v`, we write `«v»` for the binary encoding of `v`. The
+length of an encoding is always available from context: either from
+a containing encoded value, or from the overall container of the data,
+which could be a file, an HTTP message, a UDP packet, etc.
 
                           «#f» = [0xA0]
                           «#t» = [0xA1]
diff --git a/preserves-binary.md b/preserves-binary.md
index cc94369..a2164e1 100644
--- a/preserves-binary.md
+++ b/preserves-binary.md
@@ -29,8 +29,10 @@ Each `Repr` starts with a tag byte, describing the kind of information
 represented.
 
 However, inspired by [argdata][], a `Repr` does *not* describe its own
-length. Instead, the surrounding context must supply the expected length
-of the `Repr`.
+length. Instead, the expected length of the `Repr` is always available
+from the surrounding context: either from a containing encoded value, or
+from the overall container of the data, which could be a file, an HTTP
+message, a UDP packet, etc.
 
 As a consequence, `Repr`s for `Compound` values store the lengths of
 their contained values. Each contained `Value` is represented as a