$('.box').hover(function () {
$('.show').show()
})
$('.show').click(function () {
$(this).toggle()
})
<div class="box">
<button>hover</button>
<div class="show"></div>
</div>
.box{
width: 100%;
height: 50px;
position: relative;
line-height: 50px;
}
.show{
width: 100%;
height: 50px;
background: red;
position: absolute;
left: 0;
top: 50px;
display: none;
}