偷梁换柱 Steal the beams and replace them with pillars
Explanation
“偷梁换柱”比喻用假的、劣质的东西来代替真的、优质的东西，暗中玩弄手段，以假乱真，蒙骗他人。
“To steal the beams and replace them with pillars” is an idiom that means to replace something real or high quality with something fake or inferior. It is also used to describe a deception or a fraud where someone secretly replaces one thing with another.
Origin Story
在古代，有一个名叫张三的木匠，他为了偷懒，想用劣质木材来建造一座房子。他找到一位顾客，说自己有上好的木材，可以帮他建造一栋坚固的房屋。顾客信以为真，就答应了。张三偷偷地将劣质木材混在好的木材中，然后开始建造房子。房子建成后，顾客发现房子摇摇欲坠，十分不牢固。他气愤地找到张三质问，张三却狡辩说自己使用的都是上好的木材，顾客不信，就请来了其他木匠来检验。其他的木匠一看便知道，张三是用劣质木材来建造的，而且还使用了偷梁换柱的手法，将好的木材偷偷换掉。顾客得知真相后，怒气冲冲地把张三赶走了，并且将他告上了官府。
Once upon a time, there was a carpenter named John who was lazy and wanted to build a house out of inferior wood. He found a customer and told him that he had high-quality wood and could build him a sturdy house. The customer believed him and agreed. John secretly mixed inferior wood with the good wood and began to build the house. After the house was finished, the customer found that the house was rickety and not very stable. He angrily confronted John, who argued that he had only used high-quality wood. The customer didn't believe him and called in other carpenters to inspect the house. The other carpenters immediately saw that John had used inferior wood and had even switched the good beams for bad ones. When the customer learned the truth, he angrily drove John away and reported him to the police.
Usage
这个成语常用来说明一些人为了自己的利益，不惜用假的、劣质的东西来代替真的、优质的东西，暗中玩弄手段，欺骗别人。
This idiom is often used to describe how someone, for their own gain, will use fake or inferior things to replace real or high-quality things, secretly using tricks to deceive others.
Examples
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他为了自己的利益，竟然敢～，用劣质材料冒充正品。
ta wei le zi ji de li yi, jing ran gan ~, yong lie zhi cai liao mao chong zheng pin.
He dared to **switch the beams and pillars** for his own benefit, using inferior materials to pass off as authentic.
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一些不法商贩，经常利用假冒伪劣商品进行～，欺骗消费者。
yi xie bu fa shang fan, jing chang li yong jia mao wei lie shang pin jin xing ~, qi pian xiao fei zhe.
Some unscrupulous merchants often use counterfeit and shoddy products to **switch the beams and pillars**, deceiving consumers.
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不要被表面现象所迷惑，要警惕那些～的伎俩。
bu yao bei biao mian xian xiang suo mi huo, yao jing ti na xie ~ de ji liao.
Don't be fooled by appearances, be wary of those **switch the beams and pillars** tricks.
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这种～的行为，是可耻的，应该受到谴责。
zhe zhong ~ de xing wei, shi ke chi de, ying gai shou dao qian ze.
This kind of **switch the beams and pillars** behavior is shameful and should be condemned.