DF . ▁Sk ins ▁can ▁also ▁be ▁made ▁out ▁of ▁hard boards . ▁ ▁A ▁led ge ▁and ▁bra ce ▁door ▁often ▁called ▁board ▁and ▁b atten ▁doors ▁are ▁made ▁from ▁multiple ▁vertical ▁bo ards ▁fixed ▁together ▁by ▁two ▁or ▁more ▁horizontal ▁tim bers ▁called ▁led ges ▁( or ▁batt ens ) and ▁sometimes ▁kept ▁square ▁by ▁additional ▁diagonal ▁tim bers ▁called ▁bra ces . ▁ ▁A ▁w icket ▁door ▁is ▁a ▁ped est rian ▁door ▁built ▁into ▁a ▁much ▁larger ▁door ▁allowing ▁access ▁without ▁requiring ▁the ▁opening ▁of ▁the ▁larger ▁door . ▁Ex amples ▁might ▁be ▁found ▁on ▁the ▁cer emon ial ▁door ▁of ▁a ▁c athedral ▁or ▁in ▁a ▁large ▁vehicle ▁door ▁in ▁a ▁gar age ▁or ▁hang ar . ▁ ▁A ▁b if old ▁door ▁is ▁a ▁unit ▁that ▁has ▁several ▁sections , ▁fol ding ▁in ▁pairs . ▁Wood ▁is ▁the ▁most ▁common ▁material , ▁and ▁doors ▁may ▁also ▁be ▁metal ▁or ▁glass . ▁B if olds ▁are ▁most ▁commonly ▁made ▁for ▁clos ets , ▁but ▁may ▁also ▁be ▁used ▁as ▁units ▁between ▁rooms . ▁Bi - fold ▁doors ▁are ▁essentially ▁now ▁doors ▁that ▁let ▁the ▁outside ▁in . ▁They ▁open ▁in ▁concert ; ▁where ▁the ▁pan els ▁fol d ▁up ▁against ▁one ▁another ▁and ▁are ▁pushed ▁together ▁when ▁opened . ▁The ▁main ▁door ▁panel ▁( o ften ▁known ▁as ▁the ▁traffic ▁door ) ▁is ▁accompanied ▁by ▁a ▁stack ▁of ▁pan els ▁that ▁fol d ▁very ▁neat ly ▁against ▁one ▁another ▁when ▁opened ▁fully , ▁which ▁almost ▁look ▁like ▁room