# Traditional Guard FIelds

Storyspace guard fields determine whether a link can be followed at any given point in the reading. Guard fields may take into account the reader’s past trajectory and actions during the reading, and have proven indispensable for large-scale narrative.

Storyspace 3 reads traditional Storyspace guard fields and automatically wraps them in a guard expression:

> traditional: `"prologue" | "yes"`

> modern: `guard("prologue" | "yes")`

With this small change, Storyspace 3 can import and perform existing Storyspace documents, and permits you to write new Storyspace hypertexts using traditional guard fields.