# Themes - Using Additional Blocks

Source: https://docs.arcxp.com/en/products/themes/themes---using-additional-blocks.html

## HTML Box - Arc Block

![rId20.png](https://docs.arcxp.com/images/learning-center/image/img-c27ed13004d4947afa1058fbf93d77a8.png) 

_Key features:_

- Can input HTML (for example, for iFrames or third-party embeds)

The HTML Box is intended for adding one-off embed codes to your pages in PageBuilder Editor. For example, you may want to add a YouTube or other social network embed. If you are only adding a couple of these across your site, it may be sufficient to use the HTML Box block rather than developing a Custom Block to display these.

> **Note:**
> 
> The HTML Box should not be used to style elements elsewhere on the page - especially other Arc XP blocks. This is not supported by Themes.

## Header - Arc Block

![rId23.png](https://docs.arcxp.com/images/learning-center/image/img-54b7dd23aa41ef56f06dcacf20c366fa.png) 

_Key features:_

- Can input text to display as a header element at different sizes

## Masthead - Arc Block

![rId26.png](https://docs.arcxp.com/images/learning-center/image/img-d21df193267bc9701d61cc8473399688.png) 

_Key features_

- Intended for display on the homepage
- Can optionally display the following elements, which are enabled through Custom Fields: Date, Tag line, Promo link, Logo

## Divider - Arc Block

![rId29.png](https://docs.arcxp.com/images/learning-center/image/img-7d1c58620a4587433711acda94d493c6.png) 

_Key features:_

- Can be placed anywhere within your layout as a horizontal rule divider
- Styles can be defined within [blocks styling](https://dev.arcxp.com/themes/developer-docs/introduction-to-themes-20-design-system-developer-guide/#themes-20-design-system-files)