Can I use bamboo poles that were used in a fence i.e tied together and then separate them for S’chach?

Thank you for your question, You may use the bamboo poles (see B'eur Halacha 629:6). If there is a metal string that connects the bamboo poles, that is a problem. Metal is not kosher for s'chach. The metal piece that holds the s'chach is called a 'maamid'-- therefore it shouldn't be used for the s'chach. However, if you use wooden poles (which are kosher for s'chach) above the s'chach that hold the s'chach in place then the metal piece is not necessary to hold the s'chach and it wouldn't be a problem. In this case you do not have to separate it from the bamboo poles. In summary: the bamboo poles are kosher. If you use wooden poles above the s'chach to hold it in place than you don't have to separate the metal string. If you don’t have wooden poles to hold the s'chach and the metal string is holding the s'chach, that would be a problem, and shouldn't be done a priori. (לכתחילה) All the best!