Re: 識穿佢槓嘢

The following is extracted from 廣州話普通話詞典:
(p.141) 槓 gong6 -- chela of a crab, lobster etc, e.g. 蟹槓.
See also p.249 lung5.
(p.249) 槓 (杠) lung5 -- [1] large chest, e.g. 樟木槓.
[2] classifier, similar to 招/套 (trick/move/device). Ex: 睇穿佢槓嘢 / 又出邊槓吖?

The following is extracted from 香港粵語詞典 (p.297):
槓 lung5 – [1] large chest.
[2] trick (詭計): 佢嗰槓嘢邊個唔知.

In short, 槓 [lung5] means “trick”, used either as a classifier or a noun.