@perry's solution is a natural progression from having styles under a class that you want to use elsewhere. To force the use of an extension when it's only being used once is too much I think, but further on we explain that **once you start copying Sass, you must DRY to an extension instead**.

Another advantage of _always nesting elements under classes_ is you will only be thinking about semantic HTML in terms of your markup, not to conform to your styles just because you've chosen to style a `h1`.

Therefore
```sass
.content
    h1
        font:
            size: 9000px
        color: #321123
```

When wanting to use elsewhere will become
```sass
%heading-1
    font:
       size: 9000px
    color: #321123

.content
    h1
        @extend %heading-1

.sidebar
    .some-thing
        @extend %heading-1
```