CART - Set up a gift wrap product
Warehouse allows you to set up a specific "gift wrap" product on the dedicated cart page. While it is called "gift wrap", it can actually be used for any "supplemental" product you'd like to offer, like a gift wrap, a totebag, samples...
To do that, you will first need to create a standard product in your Shopify admin. Once the product is created, open the theme editor and choose "Cart" in the page selector:
Then, click on the "Cart page" section:
In the "gift wrap" sub-section, choose your product and optionally configure the wording you want to use:
By default, the theme will show a quantity selector even on the gift wrap product. To prevent the quantity selector to be shown, simply add the special tag __gift (make sure that it starts with two consecutive underscores!) to your product, and then the theme will automatically hide the quantity selector. Adding this tag will also prevent the product to be searchable and the product page to be accessible.