CSS : get a button overlapped by a div,z-index not working

Question

Fiddle Example

Can anyone figure out how to get the button overlapped by flyout-content so that the right border of the button is hidden ? I want to get this effect:

I have tried changing the z-index of the content and the button, however it doesn't work.

HTML

<div class='flyout'>
  <button class="flyout-toggle">Click</button>
  <div class="flyout-content"></div>
</div>

CSS

.flyout-toggle {
    position: absolute;
    transform: rotate(90deg);
    top: 50%;
    left: -50px;
    z-index: 998;
    width: 85px;
    height: 35px;
    font-size: 13px;
    background: #92C7B8;
    border: solid #fff 1px;
}
.flyout-content {
    z-index:997
}
.flyout {
    position: fixed;
    z-index: 999;
    top: 0;
    right: 0;
    width: 15%;
    height: 100%;
    border-left: solid #fff 1px;
    background: #92C7B8;
    -webkit-box-shadow: 0px -5px 15px 0px #bfbfbf;
    box-shadow: 0px -5px 15px 0px #bfbfbf;
    transition: all .3s ease-in-out;
}

Answer 1

jus add this border:none;

.flyout-toggle {
    background: none repeat scroll 0 0 #92c7b8;
    border: medium none;
    font-size: 13px;
    height: 35px;
    left: -50px;
    position: absolute;
    top: 50%;
    transform: rotate(90deg);
    width: 85px;
    z-index: 998;
}

but if you need a border you can add it where you need ie border-top border-left border-right; like this DEMO

Answer 2

You can use border-top: none and outline: none:

.flyout-toggle {
    position: absolute;
    transform: rotate(90deg);
    top: 50%;
    left: -60px;
    z-index: 998;
    width: 85px;
    height: 35px;
    font-size: 13px;
    background: #92C7B8;
    border: solid #fff 1px;
    border-top: none;
    outline: none;
}

fiddle