dummy up

Verb

 * 1) To make a mock-up or prototype version of something, without some or all off its intended functionality.
 * The carpenters dummied up a set of simple props for the rehearsals.
 * 1) To make a fake version of something; to make a counterfeit.
 * 2)  To suddenly stop talking; shut up; to keep a secret; to refuse to talk.
 * When he couldn't think of any more good lies, he just dummied up.
 * Everyone was discussing the new teacher, but when she entered the room they all dummied up.