.resizer {
  position: absolute;
  top: 0;
  width: 4px;
  height: 100%;
  background-color: #aaa;
  outline: solid 1px #000;
  cursor: ew-resize;
}


.resizable-container.direction-right {
  position: relative;
  margin-right: 4px;
}

.resizable-container.direction-left {
  position: relative;
  margin-left: 4px;
}


.resizable-container.direction-right .resizer {
  right: -4px;
}


.resizable-container.direction-left .resizer {
  left: -4px;
}