▁all ▁cores ▁require ▁vent ▁holes ▁to ▁release ▁g ases . ▁These ▁are ▁usually ▁formed ▁by ▁using ▁small ▁w ires ▁to ▁create ▁holes ▁from ▁the ▁surface ▁of ▁the ▁m old ▁to ▁the ▁core . ▁When ▁this ▁is ▁not ▁feas ible ▁c inder ▁and ▁co ke ▁can ▁be ▁added ▁to ▁the ▁core ▁to ▁increase ▁per me ability . ▁ ▁Chap lets ▁ ▁If ▁F ub ≤ 0 , ▁no ▁chap let ▁is ▁used . ▁ ▁If ▁F ub > 0 , ▁chap lets ▁is ▁used . ▁ ▁As ▁mentioned ▁earlier , ▁cores ▁are ▁usually ▁supported ▁by ▁two ▁core ▁prints ▁in ▁the ▁m old . ▁However , ▁there ▁are ▁situations ▁where ▁a ▁core ▁only ▁uses ▁one ▁core ▁print ▁so ▁other ▁means ▁are ▁required ▁to ▁support ▁the ▁cant ile ver ed ▁end . ▁These ▁are ▁usually ▁supplied ▁in ▁the ▁form ▁of ▁chap lets . ▁These ▁are ▁small ▁metal ▁supports ▁that ▁bridge ▁the ▁gap ▁between ▁the ▁m old ▁surface ▁and ▁the ▁core . ▁Since ▁the ▁chap lets ▁become ▁part ▁of ▁the ▁casting , ▁the ▁chap lets ▁must ▁be ▁of ▁the ▁same ▁or ▁similar ▁material ▁as ▁the ▁metal ▁being ▁cast . ▁Moreover , ▁their ▁design ▁must ▁be ▁optimized ▁because ▁if ▁they ▁are ▁too ▁small ▁they ▁will ▁completely ▁m elt ▁and ▁allow ▁the ▁core ▁to ▁move , ▁but ▁if ▁they ▁are ▁too ▁big ▁then ▁their ▁whole ▁surface ▁cannot ▁m elt ▁and ▁f use ▁with ▁the ▁pou red ▁metal . ▁Their ▁use ▁should ▁also ▁be ▁minim ized ▁because ▁they ▁can ▁cause ▁casting ▁defect s ▁or ▁create ▁weak ▁sp ots ▁in ▁the