A Rune of Teleportation is a player made tool that creates a portal to an active Teleport Stone. It is made with 2 Sigma Fragments, and requires a Workbench.

When the player uses a Rune of Teleportation, a portal is created where the player stands. The other portal will appear above an active Teleport Stone. Only one stone can be active at a time. The portal will stay open for 5 minutes, and can be made anywhere aside from NPC built structures, like the Settlement. The portal can be used by standing near it and pressing the action key.

Rune of Teleportation - Crafting Screen
Rune of Teleportation - Portal

Active Teleport Stone and Portal.