扎铁，Reinforcement Fixing，是土木工程的一个专项工序，工作内容是在待建的建筑物之混凝土墙内，先建一个由钢筋及铁线扎成的架（粤语俗称「花笼」），给予这些建筑物重力墙有更强的承重能力。整个工序非常危险，而且极须用力，是一种很吃苦的地盘前线职业，三行工人中有身体健康弱者，常见有中暑等工业意外。负责这项建筑工艺的工人（粤语又俗称为「紥铁佬」），不但要身体强健，更加要日晒雨淋。在夏天，猛烈的阳光之下，铁枝是赤热的，工人之苦可见一斑。

扎铁后的工序是「钉木板」及「下混凝土」。

A steel fixer (UK, ironworkers or "rod busters" in the United States) is a tradesman who positions and secures steel reinforcing bars, also known as rebar, and steel mesh used in reinforced concrete on construction projects.

The work involves following engineering drawings that detail the type of bar and the spacing used and setting out the work. The reinforcing bars are tied together with wire, which is cut using nips, or electric rebar tiers. Steel fixers are also responsible for attaching 'spacers' and 'chairs' that determine the amount of concrete cover.