Step 1: Recall the safety arrangement in Koepe winding.
In a Koepe winding system, overwinding is prevented by a special arrangement at the headgear.
Step 2: Identify the safety feature.
The guides are made to converge near the top so that the conveyance is gradually stopped before overwinding occurs.
Hence,
\[
\boxed{\text{Convergence of guides}}
\]
is the correct answer.
Therefore,
\[
\boxed{(C)}
\]
is the correct answer.