What's the meaning of 預約拘捕(Arrest by Appointment)?
It's not a poster.

根據官方香港電台「通識網」解釋，預約拘捕是指執法人員在有證據懷疑一個人違法或有拘捕令的情況下，預先通知及約定對方將會被捕的司法程序。
實際在執行過程中，警方會事先表明拘捕的理由及涉案人士觸犯的法律，在考慮對方不會潛逃或毀滅證據下，進行有秩序的預約拘捕，可讓對方有足夠的心理 (sic) 準備，減少因突然拘捕而出現衝突。

According to the description given by liberalstudies.hk, an &quot;Arrest by Appointment&quot; refers to the judicial procedure whereby a law-enforcement officer who, either [through having enough evidence to suspect the conduct of illegal activity] or [having an arrest warrant], gives prior notice to an individual and makes an appointment with them for their arrest.
In reality, the police will first give notice of the reason(s) for arrest and the legal case for the offence, and, under an operating assumption that the suspected individual will not attempt to destroy evidence or flee, they will conduct a lawful &quot;Arrest by Appointment&quot; procedure, allowing the suspected individual to prepare themselves for the arrest, minimising the potential shock of an otherwise sudden arrest.

(NB: This is not legal advice)