skelf kself seklf esklf keslf ekslf sklef kslef slkef lskef klsef lksef selkf eslkf slekf lsekf elskf leskf kelsf eklsf klesf lkesf elksf leksf skefl ksefl sekfl eskfl kesfl eksfl skfel ksfel sfkel fskel kfsel fksel sefkl esfkl sfekl fsekl efskl feskl kefsl ekfsl kfesl fkesl efksl feksl sklfe kslfe slkfe lskfe klsfe lksfe skfle ksfle sfkle fskle kfsle fksle slfke lsfke sflke fslke lfske flske klfse lkfse kflse fklse lfkse flkse selfk eslfk slefk lsefk elsfk lesfk seflk esflk sfelk fselk efslk feslk slfek lsfek sflek fslek lfsek flsek elfsk lefsk eflsk felsk lfesk flesk kelfs eklfs klefs lkefs elkfs lekfs kefls ekfls kfels fkels efkls fekls klfes lkfes kfles fkles lfkes flkes elfks lefks eflks felks lfeks fleks
Note: these 'words' (valid or invalid) are all the permutations of the word skelf. These words are obtained by scrambling the letters in skelf.