The trustees shall have authority to appoint annually and to prescribe the duties of a Chief of Police and police officers; of a Chief Engineer of the Fire Department and the assistant engineers; of the superintendents of the Village departments; of a Building Inspector; and of such other Village officials as they may judge necessary for the welfare of the Village; and the number of police officers, engineers, and Village firemen and other employees shall be within the discretion of the said trustees. Such of these officers as the trustees may direct shall be qualified by taking appropriate oaths of office, and their appointments and the certificates of their oaths shall be recorded by the Village Clerk. Said appointments may be revoked at the pleasure of the trustees, and the trustees may make rules and regulations governing the activities of these officers and of all other Village employees.