▁parts ▁of ▁it , ▁making ▁repair ▁une conom ic . ▁The ▁attack ▁reports ▁below ▁should ▁be ▁considered ▁with ▁this ▁in ▁mind . ▁ ▁An ▁alternative ▁technique ▁was ▁to ▁ar range ▁det on ation ▁depth ▁so ▁that ▁the ▁cr ater ▁broke ▁the ▁surface — use ful ▁for ▁attack ing ▁railway ▁mar sh alling ▁yards ▁and ▁similar ▁targets . ▁The ▁T all boy ▁produced ▁an ▁ 8 0   ft ▁cr ater ▁with ▁depth s ▁up ▁to ▁ 1 0 0   ft , ▁unlike ▁conventional ▁bomb s ▁which ▁would ▁produce ▁many ▁shall ow ▁cr aters ▁across ▁a ▁target — each ▁one ▁of ▁which ▁could ▁later ▁be ▁filled ▁in ▁rapidly ▁with ▁earth - mov ing ▁equipment . ▁Such ▁a ▁huge ▁hole ▁was ▁time - consum ing ▁to ▁fill ; ▁multiple ▁tr uck s ▁and ▁bul ld oz ers ▁could ▁not ▁be ▁fitted ▁around ▁the ▁peri ph ery ▁of ▁the ▁hole ▁to ▁speed ▁the ▁process . ▁ ▁Man ufact uring ▁The ▁construction ▁of ▁each ▁T all boy ▁was ▁labour ▁int ensive ▁because ▁each ▁was ▁largely ▁hand - made , ▁requiring ▁much ▁manual ▁labour ▁during ▁each ▁separate ▁manufact uring ▁stage . ▁The ▁materials ▁used ▁were ▁cost ly , ▁with ▁very ▁precise ▁engineering ▁requirements ▁with ▁regard ▁to ▁casting ▁and ▁mach ining . ▁For ▁example , ▁to ▁increase ▁pen etr ative ▁power , ▁a ▁large ▁and ▁spe cially ▁hard ened ▁steel ▁plug ▁had ▁to ▁be ▁precisely ▁mach ined ▁and ▁m ated ▁to ▁a ▁re cess ▁in ▁the ▁nose ▁of ▁the ▁bomb . ▁The ▁og ive ▁had ▁to ▁be ▁mach