When can a Skater be sent to the Penalty Box as a substitute for a fouled-out Skater?

A skater can only be sent to the penalty box to substitute for a fouled-out skater when the jam is over. This is because the playing environment requires that substitutions occur during designated breaks in the action, which is the end of a jam. The rules of roller derby maintain that all player movements must be orderly and respect the game’s flow to ensure fair play and minimize disruption. Allowing immediate substitution as soon as a skater fouls out would create confusion on the track and could lead to unsanctioned advantages, thus the structured timing at the end of a jam is critical.

For clarity, while it's important to recognize when a skater is fouled out, the actual replacement cannot take place until an official stoppage in play, which occurs at the end of the jam.