CSS：

.check {
    width: 40px;
    height: 80px;
    outline: 1px solid red;
    position: relative;
}
.center {
    margin: 0;
    position: absolute;
    top: 50%;
    left: 50%;
    margin-left: -.5em;
    margin-top: -.5em;
}

JSFiddle：http://jsfiddle.net/Yzhnf/4/