kerfs ekrfs krefs rkefs erkfs rekfs kefrs ekfrs kfers fkers efkrs fekrs krfes rkfes kfres fkres rfkes frkes erfks refks efrks ferks rfeks freks kersf ekrsf kresf rkesf erksf reksf kesrf eksrf kserf skerf eskrf sekrf krsef rksef ksref skref rskef srkef erskf reskf esrkf serkf rsekf srekf kefsr ekfsr kfesr fkesr efksr feksr kesfr eksfr ksefr skefr eskfr sekfr kfser fkser ksfer skfer fsker sfker efskr feskr esfkr sefkr fsekr sfekr krfse rkfse kfrse fkrse rfkse frkse krsfe rksfe ksrfe skrfe rskfe srkfe kfsre fksre ksfre skfre fskre sfkre rfske frske rsfke srfke fsrke sfrke erfsk refsk efrsk fersk rfesk fresk ersfk resfk esrfk serfk rsefk srefk efsrk fesrk esfrk sefrk fserk sferk rfsek frsek rsfek srfek fsrek sfrek
Note: these 'words' (valid or invalid) are all the permutations of the word kerfs. These words are obtained by scrambling the letters in kerfs.