▁Fl ush ▁doors ▁ ▁Many ▁modern ▁doors , ▁including ▁most ▁interior ▁doors , ▁are ▁flush ▁doors : ▁ ▁St iles ▁and ▁rails ▁– ▁As ▁above , ▁but ▁usually ▁smaller . ▁They ▁form ▁the ▁outside ▁edges ▁of ▁the ▁door . ▁ ▁Core ▁material : ▁Material ▁within ▁the ▁door ▁used ▁simply ▁to ▁fill ▁space , ▁provide ▁rig id ity ▁and ▁reduce ▁drum min ess . ▁ ▁H ollow - core ▁– ▁O ften ▁consists ▁of ▁a ▁lattice ▁or ▁h oney comb ▁made ▁of ▁cor rug ated ▁card board , ▁or ▁thin ▁wooden ▁sl ats . ▁Can ▁also ▁be ▁built ▁with ▁st agger ed ▁wooden ▁blocks . ▁H ollow - core ▁flush ▁doors ▁are ▁commonly ▁used ▁as ▁interior ▁doors . ▁ ▁Lock ▁block ▁– ▁A ▁solid ▁block ▁of ▁wood ▁mounted ▁within ▁a ▁h ollow - core ▁flush ▁door ▁near ▁the ▁b olt ▁to ▁provide ▁a ▁solid ▁and ▁stable ▁location ▁for ▁mount ing ▁the ▁door ' s ▁hardware . ▁ ▁St ave - core ▁– ▁Cons ists ▁of ▁wooden ▁sl ats ▁stack ed ▁upon ▁one ▁another ▁in ▁a ▁manner ▁similar ▁to ▁a ▁board ▁and ▁b atten ▁door ▁( though ▁the ▁sl ats ▁are ▁usually ▁th inner ) ▁or ▁the ▁wooden - block ▁h ollow - core ▁( except ▁that ▁the ▁space ▁is ▁entirely ▁filled ). ▁ ▁Sol id - core ▁– ▁Can ▁consist ▁of ▁low - dens ity ▁particle ▁board ▁or ▁fo am ▁used ▁to ▁completely ▁fill ▁the ▁space ▁within ▁the ▁door . ▁Sol id - core ▁flush ▁doors ▁( es pecially ▁fo am - core ▁ones