When they join the Party, new members raise their right hands and take the oath facing the Party flag.
Tips
culture
In the PRC 入党 means joining the Communist Party unless another party is named. The main steps are a written application (入党申请书), a year as a probationary member (预备党员), then full membership.
grammar
入党 is a separable verb: 入了党, 入过党. The opposite is 退党 'to leave the party'.