shack hsack sahck ashck hasck ahsck shcak hscak schak cshak hcsak chsak sachk aschk scahk csahk acshk cashk hacsk ahcsk hcask chask achsk cahsk shakc hsakc sahkc ashkc haskc ahskc shkac hskac skhac kshac hksac khsac sakhc askhc skahc ksahc akshc kashc haksc ahksc hkasc khasc akhsc kahsc shcka hscka schka cshka hcska chska shkca hskca skhca kshca hksca khsca sckha cskha skcha kscha cksha kcsha hcksa chksa hkcsa khcsa ckhsa kchsa sackh asckh scakh csakh acskh caskh sakch askch skach ksach aksch kasch sckah cskah skcah kscah cksah kcsah acksh caksh akcsh kacsh ckash kcash hacks ahcks hcaks chaks achks cahks hakcs ahkcs hkacs khacs akhcs kahcs hckas chkas hkcas khcas ckhas kchas ackhs cakhs akchs kachs ckahs kcahs
Note: these 'words' (valid or invalid) are all the permutations of the word shack. These words are obtained by scrambling the letters in shack.