TRBL

1. top right bottom left
2. Or, clockwise

CSS

.trbl_4 {
    border-style: solid;
    border-width: 2em;
    border-color: red green blue black;
} 

.trbl_4 {
    width: 10%;
    height: 3em;
    text-align: center;
    border-style: solid;
    border-width: 2em;
    border-color: red green blue black;
    display: table-cell;
    vertical-align: middle;
} 

1. top-(left,right)-bottom
2. mnemonic: left, right step together
3. (Step together boldly tread)

CSS

.t_lr_b_3 {
    border-style: solid;
    border-width: 2em;
    border-color: red green blue;
} 

.t_lr_b_3 {
    width: 20%;
    height: 3em;
    text-align: center;
    border-style: solid;
    border-width: 2em;
    border-color: red green blue;
    display: table-cell;
    vertical-align: middle;
} 

1. (top,bottom)–(left,right)
2. But note that (table) border-spacing behaves as
   (left,right)–(top,bottom)

CSS

.tb_lr_2 {
    border-style: solid;
    border-width: 2em;
    border-color: red blue;
} 

.tb_lr_2 {
    width: 20%;
    height: 3em;
    text-align: center;
    border-style: solid;
    border-width: 2em;
    border-color: red blue;
    display: table-cell;
    vertical-align: middle;
} 

(left,right)–(top,bottom)

CSS

.t_bs,
.t_bs th,
.t_bs td {
    border: 1px solid green;
    border-spacing: 1px 30px;
} 

1. For 4 CSS properites, TRBL or clockwise
2. For 3 CSS properties, left, right step together