<a href="#" class="cp_btn">button</a>

a.cp_btn {
  position: relative;
  display: block;
  width: 160px;
  padding: 0.8em;
  text-align: center;
  font-weight: bold;
  text-decoration: none;
  color: #2196F3;
  transition: .4s;
}
a.cp_btn:before,
a.cp_btn:after {
  position: absolute;
  top: 0;
  content: '';
  width: 4px;
  height: 100%;
  border-radius: 3px;
  background:#2196F3;
  transition: .2s ease-in;
}
a.cp_btn:before {
  left: 0;
}
a.cp_btn:after {
  left: 100%;
}
a.cp_btn:hover:before,
a.cp_btn:hover:after {
  transform: rotate(20deg);
}