GUIStyle.border

Description

The borders of all background images.

This corresponds to the border settings for IMGUI elements. It only affects the rendering of the background image and has no effect on positioning.

using UnityEngine;

public class Example : MonoBehaviour
{
    // Prints the left, right, top and down values of the GUIStyle border

    RectOffset bdr;
    void OnGUI()
    {
        bdr = GUI.skin.button.border;
        Debug.Log("Left: " + bdr.left + " Right: " + bdr.right);
        Debug.Log("Top: " + bdr.top + " Bottom: " + bdr.bottom);
    }
}