Why a line stops moving

A number sitting still through heavy action usually means the book is comfortable holding that side, not that it has stopped paying attention.

Moving a line is a decision with a cost — it changes the exposure on both sides and can invite further action. A book confident in its number simply declines to pay that cost.

Sometimes a line does not move because nothing worth reacting to has happened, which is the boring and most common explanation.

Here is the catch. Stillness reads as inattention and is usually the opposite, which leads readers to expect an opportunity where the book has made a firm decision.

What to do with it. Read a stationary line at a key number as a statement of confidence rather than as an oversight.