.sidebar {
  position: fixed;
  top: 0;
  bottom: 0;
  left: 0;
  z-index: 100; /* Behind the navbar */
  padding: 70px 0 0; /* Height of navbar */
  box-shadow: inset -1px 0 0 rgba(0, 0, 0, .1);
}

.sidebar-sticky {
  position: relative;
  top: 0;
  height: calc(100vh - 48px);
  padding-top: .5rem;
  overflow-x: hidden;
  overflow-y: auto; /* Scrollable contents if viewport is shorter than content. */
}

@supports ((position: -webkit-sticky) or (position: sticky)) {
  .sidebar-sticky {
    position: -webkit-sticky;
    position: sticky;
  }
}

.anchor .a {
  position: absolute;
  left: 0px;
  top: -4.5rem;
}

.anchor {
  position: relative;
}