1. You can find No. 20 I-beam in the following ways.

2. First, you can look for it in the local steel market or building materials market, which usually has steel supplies of various specifications. Secondly, you can search and purchase through Internet platforms, such as Alibaba, JD.com and other e-commerce platforms or steel trading platforms. Finally, you can contact local steel mills or steel trading companies, they usually have inventory or can customize production.

3. Before looking for No. 20 I-beam, you need to understand the specifications and quantity you need so that you can choose suppliers and purchase methods more accurately. At the same time, when purchasing steel, you need to pay attention to quality and price, and choose suppliers with good reputation and reasonable prices.