Present participle; Past participle - clacking - clacked Present - clack - clack - clacks - clack - clack - clack Past - clacked - clacked - clacked - clacked - clacked - clacked Future - will clack - will clack - will clack - will clack - will clack - will clack Present conditional - would clack - would clack - would clack - would clack - would clack - would clack Present Perfect - have clacked - have clacked - has clacked - have clacked - have clacked - have clacked Past Perfect - had clacked - had clacked - had clacked - had clacked - had clacked - had clacked Future Perfect - will have clacked - will have clacked - will have clacked - will have clacked - will have clacked - will have clacked Past conditional - would have clacked - would have clacked - would have clacked - would have clacked - would have clacked - would have clacked Imperative - - - clack - - - - - - - -