▁dock ing ▁tunnel . ▁It ▁was ▁ ▁in ▁diameter ▁and ▁we ighed ▁. ▁It ▁was ▁constructed ▁from ▁two ▁mach ined ▁rings ▁that ▁were ▁w eld - jo ined ▁to ▁a ▁bra zed ▁h oney comb ▁panel . ▁The ▁exterior ▁side ▁was ▁covered ▁with ▁a ▁ ▁of ▁ins ulation ▁and ▁a ▁layer ▁of ▁al umin um ▁fo il . ▁It ▁was ▁l atch ed ▁in ▁six ▁places ▁and ▁operated ▁by ▁a ▁p ump ▁handle . ▁The ▁h atch ▁contained ▁a ▁val ve ▁in ▁its ▁center , ▁used ▁to ▁equal ize ▁the ▁pressure ▁between ▁the ▁tunnel ▁and ▁the ▁C M ▁so ▁the ▁h atch ▁could ▁be ▁removed . ▁ ▁The ▁un ified ▁crew ▁h atch ▁( U CH ) ▁measured ▁ ▁high , ▁ ▁wide , ▁and ▁we ighed ▁. ▁It ▁was ▁operated ▁by ▁a ▁p ump ▁handle , ▁which ▁drove ▁a ▁r atch et ▁mechanism ▁to ▁open ▁or ▁close ▁fifteen ▁l atch es ▁simultaneously . ▁ ▁D ock ing ▁assembly ▁Apol lo ' s ▁mission ▁required ▁the ▁L M ▁to ▁dock ▁with ▁the ▁C SM ▁on ▁return ▁from ▁the ▁Moon , ▁and ▁also ▁in ▁the ▁trans position , ▁dock ing , ▁and ▁extra ction ▁man eu ver ▁at ▁the ▁beginning ▁of ▁the ▁transl un ar ▁coast . ▁The ▁dock ing ▁mechanism ▁was ▁a ▁non - and rog yn ous ▁system , ▁consisting ▁of ▁a ▁pro be ▁located ▁in ▁the ▁nose ▁of ▁the ▁C SM , ▁which ▁connected ▁to ▁the ▁dro gue , ▁a ▁trunc ated ▁cone ▁located ▁on ▁the ▁lun ar ▁module . ▁The