Place block script

I had put the break/place block script in my engine and when i right clicked for placing a block i got a huge gaping hole in the ground, breaking blocks with the left click works fine, Can i get a little help? This is the code..

 <p>var blockLayer : LayerMask = 1;
 var range : float = Mathf.Infinity;
 var hit : RaycastHit;</p>
 
 <p>function Update () {
     if (Input.GetMouseButtonDown(0))
         Build();
     if (Input.GetMouseButtonDown(1))
         Erase();
 }</p>
 
 <p>function Build() {
     if (HitBlock()) {
         var cube = GameObject.CreatePrimitive(PrimitiveType.Cube);
         cube.transform.position = hit.transform.position + hit.normal;
     }
 }</p>
 
 <p>function Erase() {
     if (HitBlock())
         Destroy(hit.transform.gameObject);
 }</p>
 
 <p>function HitBlock() : boolean {
     return Physics.Raycast(transform.position, transform.forward, hit, range, blockLayer);
 }</p>