The column-rule-width CSS property sets the thickness of the line that is drawn between columns by column-rule-style in a CSS multi-column layout.
.columns {
columns: 2 600px;
column-rule-style: dotted;
column-rule-width: 3px;
}Another way to go about it is to use the column-rule shorthand property, which combines column-rule-width, column-rule-style and column-rule-color.
.columns {
columns: 2 600px;
column-rule: dotted 3px #f8a100;
}column-rule-width: thin | medium | thick | <length>medium0 if the column-rule-style is none or hiddencolumn-rule-width takes a single named, length or global value.
/* Named values */
column-rule-width: thin;
column-rule-width: medium;
column-rule-width: thick;
/* Length values */
column-rule-width: 15px;
column-rule-width: 1.5rem;
/* Global values */
column-rule-width: inherit;
column-rule-width: initial;
column-rule-width: unset;column-countcolumn-fillcolumn-gapcolumn-rulecolumn-rule-colorcolumn-rule-stylecolumn-spancolumn-widthcolumnsCSS Multi-column Layout Module Level 1 (Editor’s Draft)