# `block`
Blocks are used for inheritance and act as placeholders and replacements atthe same time. They are documented in detail in the documentation for the[*extends*](#) tag.
Block names should consist of alphanumeric characters, and underscores. Dashesare not permitted.
See also
[*block*](#), [*parent*](#), [*use*](#), [*extends*](#)
- Twig
- Introduction
- Installation
- Twig for Template Designers
- Twig for Developers
- Extending Twig
- Twig Internals
- Deprecated Features
- Recipes
- Coding Standards
- Tags
- autoescape
- block
- do
- embed
- extends
- filter
- flush
- for
- from
- if
- import
- include
- macro
- sandbox
- set
- spaceless
- use
- verbatim
- Filters
- abs
- batch
- capitalize
- convert_encoding
- date
- date_modify
- default
- escape
- first
- format
- join
- json_encode
- keys
- last
- length
- lower
- merge
- nl2br
- number_format
- raw
- replace
- reverse
- round
- slice
- sort
- split
- striptags
- title
- trim
- upper
- url_encode
- Functions
- attribute
- block
- constant
- cycle
- date
- dump
- include
- max
- min
- parent
- random
- range
- source
- template_from_string
- Tests
- constant
- defined
- divisible by
- empty
- even
- iterable
- null
- odd
- same as