/*.col-md-3 {
  position: relative;
  display: inline-block;
  border-bottom: 1px dotted black;
}*/

.col-md-3 .tool {
  visibility: hidden;
  width: 250px;
  background-color: #555;
  color: #fff;
  text-align: center;
  border-radius: 6px;
  padding: 5px 0;
  position: absolute;
  top: -15%;
  z-index: 1;
  /*bottom: 125%;*/
  left: 30%;
  margin-left: -60px;
  opacity: 0;
  transition: opacity 0.3s;
}

.col-md-3 .tool::after {
  content: "";
  position: absolute;
  top: 100%;
  left: 50%;
  margin-left: -5px;
  border-width: 5px;
  border-style: solid;
  border-color: #555 transparent transparent transparent;
}

.col-md-3:hover .tool {
  visibility: visible;
  opacity: 1;
}