.fixed-at-side {
    width: 100%;
    height: 100%;
    border: 1px solid rgba(0, 0, 0, .3);
    border-radius: 0.25rem;

    position: relative;
}

.fixed-at-side__side {
    height: 40%;
    position: absolute;    
    top: 50%;
    transform: translate(0px, -50%);
}
.fixed-at-side__side--l {
    left: 0;
}
.fixed-at-side__side--r {
    right: 0;
}