es ▁it ▁has ▁a ▁mechanism , ▁often ▁counter bal anced ▁or ▁spr ung , ▁that ▁allows ▁it ▁to ▁be ▁lifted ▁so ▁that ▁it ▁rest s ▁hor izont ally ▁above ▁the ▁opening . ▁A ▁roll er ▁sh utter ▁or ▁section al ▁overhead ▁door ▁is ▁one ▁variant ▁of ▁this ▁type . ▁ ▁A ▁tamb our ▁door ▁or ▁roll er ▁door ▁is ▁an ▁up - and - over ▁door ▁made ▁of ▁narrow ▁horizontal ▁sl ats ▁and ▁" roll s " ▁up ▁and ▁down ▁by ▁sl iding ▁along ▁vertical ▁tracks ▁and ▁is ▁typically ▁found ▁in ▁entertain ment ▁cent res ▁and ▁cabin ets . ▁ ▁In ward ▁opening ▁doors ▁are ▁doors ▁that ▁can ▁only ▁be ▁opened ▁( or ▁forced ▁open ) ▁from ▁outside ▁a ▁building . ▁Such ▁doors ▁pose ▁a ▁substantial ▁fire ▁risk ▁to ▁occup ants ▁of ▁occupied ▁buildings ▁when ▁they ▁are ▁locked . ▁As ▁such ▁doors ▁can ▁only ▁be ▁forced ▁open ▁from ▁the ▁outside , ▁building ▁occup ants ▁would ▁be ▁prevent ed ▁from ▁esc aping . ▁In ▁commercial ▁and ▁ret ail ▁situations ▁manufact ur ers ▁have ▁included ▁in ▁the ▁design ▁a ▁mechanism ▁that ▁allows ▁an ▁in ward ▁opening ▁door ▁to ▁be ▁pushed ▁open ▁out wards ▁in ▁the ▁event ▁of ▁an ▁emer gency ▁( which ▁is ▁often ▁a ▁regul atory ▁requirement ). ▁This ▁is ▁known ▁as ▁a ▁' break away ' ▁feature . ▁P ushing ▁the ▁door ▁out ward ▁at ▁its ▁closed ▁position , ▁through ▁a ▁switch ▁mechanism , ▁dis connect s ▁power ▁to ▁the ▁l atch ▁and ▁allows ▁the ▁door ▁to ▁swing ▁out ward . ▁Upon ▁returning