There are many synonyms for the phrase "put guard," which refers to protecting or securing something from harm or danger. Some synonyms for this phrase include "set up defense," "establish protection," "create a barricade," "fortify," "safeguard," and "defend." Depending on the context in which this phrase is used, other synonyms may include terms like "secure," "enclose," "shield," "guard," "cover," "armor," "armor up," and "protect." All of these synonyms convey the same general idea of taking steps to protect something or someone from potential harm or danger, and can be used interchangeably in most cases.