src/elements/Rail/Rail.js
function Rail(props) {
  const {
    attached,
    children,
    className,
    close,
    content,
    dividing,
    internal,
    position,
    size,
  } = props

  const classes = cx(
    'ui',
    position,
    size,
    useKeyOnly(attached, 'attached'),
    useKeyOnly(dividing, 'dividing'),
    useKeyOnly(internal, 'internal'),
    useKeyOrValueAndKey(close, 'close'),
    'rail',
    className,
  )
  const rest = getUnhandledProps(Rail, props)
  const ElementType = getElementType(Rail, props)

  return (
    <ElementType {...rest} className={classes}>
      {childrenUtils.isNil(children) ? content : children}
    </ElementType>
  )
}
function Rail(props) {
  const {
    attached,
    children,
    className,
    close,
    content,
    dividing,
    internal,
    position,
    size,
  } = props

  const classes = cx(
    'ui',
    position,
    size,
    useKeyOnly(attached, 'attached'),
    useKeyOnly(dividing, 'dividing'),
    useKeyOnly(internal, 'internal'),
    useKeyOrValueAndKey(close, 'close'),
    'rail',
    className,
  )
  const rest = getUnhandledProps(Rail, props)
  const ElementType = getElementType(Rail, props)

  return (
    <ElementType {...rest} className={classes}>
      {childrenUtils.isNil(children) ? content : children}
    </ElementType>
  )
}
A rail is used to show accompanying content outside the boundaries of the main view of a site.