清廷对紫禁城乃至北京城各门的管理和启闭,都有严格的规章制度。特别是在夜间,更不能随意出入,如果有要事急需出入者,就得凭一种特殊的出门证,纔可启开城门放行。这种特殊出门证,称合符。合符系铜制,由阴阳两扇组成,每一扇里侧分别铸有阳文和阴文“圣旨”二字,阴阳合一,浑然一体。故 The Qing court has strict rules and regulations on the management and opening and closing of the various gateways in the Forbidden City and even in Beijing. Especially at night, but also can not arbitrarily access, if there is an urgent need to move in, you have to go by a special permit to open the gate release. This special exit card, said coincidence. Coincidentally the Department of copper, composed of two yin and yang, each side of the fan were cast in Yangwen and Yinwen “imperial edict” word, yin and yang unity, seamless. Therefore