strategic placement

A sister closed in on him, swinging a lit torch. A softball-sized rock of ice came flying at
him from behind her. He continued to dodge them, holding Orsola close. He soon
spotted metal construction-pipe scaffolding surrounding the long and thin Church of
Confirmation, which was behind the Church of Matrimony, and dashed up in bounds.
He used the slanted rungs to run up to the second floor. The torch-holding sister
carelessly came after him—he kicked her down to the ground with his right foot. A
moment later, another sister somehow jumped from the ground up to where he was
with a single leap; as she set foot on the unstable scaffolding, Kamijou swept her legs out
and sent her tumbling back down.
“—”
The eyes of dozens of sisters on the ground stared up at him on the scaffolding,
observing him mechanically.
They would have realized by now.
They could surround him with dozens of people and attack all at once—they wouldn’t
have anywhere to run then. But if he found a place where they needed to fight one-on-
one, he could pick out an escape route.

The metal pipes making up the scaffolding he stood on were long, thin, and unstable, so
the sisters couldn’t deliver a unified attack from all directions. If they were to follow him
up the narrow scaffolding, they would inevitably need to get in a neat single-file line. In
fact, if that many people all ran onto the scaffolding, it would buckle under their weight
and collapse. Unless they were prepared to die, they couldn’t use their numbers to their
advantage because of the sacrifice it might require.
The sisters in jet-black pondered on what that meant...

- Toaru Majustsu no Index Volume 7, Chapter 4 Part 1