.lock{
  width:195px;
  height:195px;
  background:no-repeat center;
  border:1px solid grey;
  display:inline-block;
  overflow:hidden;
}

.lock a{
  width:55px;
  height:55px;
  display:inline-block;
  background:url(../images/dot-off.png) no-repeat center;
  margin:5px;
  float:left;
  text-decoration:none;
}

.lock a.active, .lock a:hover{
  background:url(../images/dot-on.png) no-repeat center;
}