fenom/docs/en/tags/extends.md

Tag {extends}

{extends} tags are used in child templates in template inheritance for extending parent templates. The {extends} tag must be on before any block. Also if a child template extends a parent template with the {extends} tag it may contain only {block} tags. Any other template content is ignored.

{extends}

{extends 'parent.tpl'}

{block}

{block 'bk2'}content 2{/block}

{use}

Import the blocks defined in another file. Specifying blocks in this template will override those from the other file.

{use 'blocks.tpl'} merge blocks from blocks.tpl template

{block 'alpha'} rewrite block alpha from blocks.tpl template, if it exists
   ...
{/block}

{parent}

Uses the code from the block as defined in the parent.

{extends 'parent.tpl'}

{block 'header'}
  content ...
  {parent}  pase code from block 'header' from parent.tpl
  content ...
{/block}

{paste}

Pastes the code of any block

{block 'b1'}
    ...
{/block}

{block 'b2'}
    ...
    {paste 'b1'} paste code from b1
{/block}

{$.block}

Checks if clock exists

{if $.block.header}
    block header exists
{/if}