div.block.with-block-editing {
  position: relative;
}

div.block.with-block-editing div.edit {
  display: none;
  position: absolute;
  right: 0; 
  top: 0;
  z-index: 40;
  border: 1px solid #eee;
  padding: 0 2px;
  font-size: 0.75em;
  background-color: #fff;
}

div.block.with-block-editing:hover div.edit {
  display: block;
}