GameObject.layer

Description

The layer the game object is in. A layer is in the range [0...31].

Layers can be used for selective rendering from cameras or ignoring raycasts.

// Put the game object in the ignore raycast layer
gameObject.layer = 2;

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    void Example() {
        gameObject.layer = 2;
    }
}