Dynamo Works

Dynamo Works is a room in Sanctuary Fortress. Spider Ball is found here.

Layers
A gate just before engaging the Spider Guardian is closed unless Samus visits Dynamo Works from the other side.

The spider ball tracks in the second and third phases of the boss fight do not function until after the boss is defeated.

The spider ball track on the non-boss side does not function until after the boss is defeated.

Boss Skip
Instant morphing into the tunnel on the non-boss side (containing the expansion) allows you to skip Spider Guardian.

This is often done alongside Item Loss Skip.

Skipping Spider Track
A bomb space jump or ghetto jump allows you to climb to the ledge on the non-boss side. This is useful if you do not have Spider Ball or have not beaten Spider Guardian.,