.sectionWrap {
    display:grid;
    grid-template-columns:100px 1fr 100px;
    grid-template-rows:600px;
    margin: 10px;
}
.sectionWrap .Ad{
    position:relative;
}


.sectionWrap section{
    background: lightblue;
    margin-left: 10px;
    margin-right: 10px;
   
}


.Ad .adbox{
    width: 100px;
    height: 600px;
    position:fixed;
    background:tomato;
}