# `lock`

```strand
element lock: surface
```

The lock screen, on `ext-session-lock`: on every monitor its
`screens:` picks (every one by default), one instance a monitor
sharing the lock's `state`s, timers and `on change` handlers. It is
exempt from reload and fails closed.

It is a surface, written at the top level of a file.

Also every prop and event of [`surface`](/reference/elements/surface.html.md).

| In scope | Type | |
| --- | --- | --- |
| `screen` | `Screen` | The monitor this instance is on; with `screens: focused` (or a pick no plugged monitor matches), the focused one, else the first, changing in place as focus moves. |