A Marker Switch is a device Atrus created for use on Myst Island. Eight of them are found throughout the island, each at an important landmark. They are used to control what landmarks are visible on the map in the Myst Library. They are also necessary to lock the Tower of Rotation on a landmark, as it will only lock onto landmarks shown on the map. Note that not all marker switch locations can be locked onto.
The marker switch near the Dock and Ship also serves as a vault. Sirrus and Achenar locked the page they took from Atrus's Myst Linking Book in K'veer in there. To open the vault, all of the marker switches would have to be switched on, and then the one with the vault would have to be switched off.
By 2005 CE, all of them have become non-operational.
- Dock and Ship
- Sunken Gears
- Pillar Garden
- Log Cabin/Tree Elevator