# ToolClass.server_onFixedUpdate

Called every game tick – 40 ticks a second. If the frame rate is lower than 40 fps, this event may be called twice.

**Kind:** Callback

**Environments:** Game

## Game

**Callback side:** Server

``` { .lua .api-signature }
ToolClass:server_onFixedUpdate( timeStep )
```

[Open the full Game reference](../Game-Script-Environment/Classes/ToolClass.md#server_onfixedupdate)

During a fixed update, physics and logic between interactables are updated.

**Parameters:**

| Name | Type | Description |
| --- | --- | --- |
| `self` | table | The class instance. |
| `timeStep` | number | The time period of a tick. (Is always 0.025, a 1/40th of a second.) |