The NLRA requires that employees must be given at least 30 days from the date of hire to join the union before they may be subject to being fired for failure to join the union or pay dues; shorter periods apply in the construction industry. The RLA gives employees 60 days to join the union. The union cannot, however, require that an employee become a member "in good standing" — that is, do more than pay dues or their equivalent. While a union shop agreement that, by its literal terms, requires an employee to become a member in good standing might appear to be unlawful on its face and therefore unenforceable, the National Labor Relations Board (NLRB) and the courts have uniformly interpreted such clauses to require no more than what the law permits (such as payment of dues).