Out of the Sandbox themes feature a framework with a 16 column base.
It’s important to distinguish, however, between those 16 base columns that the framework defines and the actual columns you are creating within that framework. The columns you create can span one or more of the base columns but still be considered a single column that "sits" on top of the base columns.
This article will refer to the columns you create as "column divisions" while the 16 base columns will always be referred to as "column base" or "base columns."
To create multiple column division layouts within Out of the Sandbox Shopify themes, use multiple <div> and </div> tags with class names that indicate how many columns, out of the total 16, you would like each column division to spread over.
To help clarify this, think of a page with a single column division as spanning across all 16 columns. A two column page, meanwhile, would have two column divisions that each span across eight columns. Because 8 (the number of base columns the division stretches over) multiplied by 2 (the number of column divisions being created) equals 16, this layout will feature two equally-sized column divisions that fill the entire width of the layout.
Within the 16 column base, you can have any number of column divisions that span over a variety of base columns as long as the total number of based columns used adds up to 16 or less.
For a shortcut to creating multiple columns with HTML check out the Out of the Sandbox Content Creator Extension for Google Chrome: