▁switch ▁when ▁the ▁kn ife ▁is ▁pushed ▁into ▁the ▁j aw . ▁Kn ife ▁switch es ▁can ▁take ▁several ▁forms , ▁including ▁single ▁throw , ▁in ▁which ▁the ▁" kn ife " ▁eng ages ▁with ▁only ▁a ▁single ▁slot , ▁and ▁double ▁throw , ▁in ▁which ▁the ▁kn ife ▁h inge ▁is ▁placed ▁between ▁two ▁sl ots ▁and ▁can ▁eng age ▁with ▁either ▁one . ▁Also , ▁multiple ▁kn ives ▁may ▁be ▁attached ▁to ▁a ▁single ▁handle ▁and ▁can ▁be ▁used ▁to ▁activ ate ▁more ▁than ▁one ▁circuit ▁simultaneously . ▁ ▁Current ▁uses ▁Though ▁used ▁commonly ▁in ▁the ▁past , ▁kn ife ▁switch es ▁are ▁now ▁rare , ▁finding ▁use ▁largely ▁in ▁science ▁experiments ▁where ▁the ▁position ▁of ▁the ▁switch ▁may ▁be ▁plain ly ▁seen ▁in ▁demonstr ation . ▁ ▁The ▁kn ife ▁switch ▁is ▁extremely ▁simple ▁in ▁construction ▁and ▁use , ▁but ▁its ▁exposed ▁metal ▁parts ▁present ▁a ▁great ▁risk ▁of ▁electric ▁shock , ▁and ▁the ▁switch ▁is ▁subject ▁to ▁ar cing ▁when ▁opened ▁at ▁higher ▁volt ages , ▁which ▁pos es ▁a ▁further ▁risk ▁of ▁shock ▁or ▁burn s ▁to ▁the ▁operator ▁and ▁ ▁can ▁cause ▁fires ▁or ▁explos ions ▁under ▁certain ▁conditions . ▁ ▁Open ▁kn ife ▁switch es ▁were ▁supp l anted ▁by ▁safety ▁switch es ▁with ▁current ▁carrying ▁contacts ▁inside ▁a ▁metal ▁en closure ▁which ▁can ▁only ▁be ▁opened ▁by ▁switching ▁off ▁the ▁power . ▁In ▁modern ▁applications , ▁automatic ▁switch es ▁( such ▁as ▁contact ors ▁or ▁rel ays ), ▁and ▁manual ▁switch es ▁such ▁as ▁circuit