Non verbs cannot directly take past tenses. The verb Proto-Turkic*er-(“to be (aux.)”) takes the past tense suffix and with it the meaning of the past tense is provided. For example;
*eb er-(“house + to be”) + *-ti → *eb erti(“(I saw/I'm sure) it was a house.”)
Contrary to modern usages, as in Old Turkic and Bulgar language, the consonants l, r and n are followed by the strong consonant form; remaining sounds are followed by the soft consonant form. For example;
Erdal, Marcel (2004), “-dI”, in A Grammar of Old Turkic (Handbook of Oriental Studies. Section 8 Uralic & Central Asian Studies; 3), Brill Academic Publishers, →ISBN, page 238
Krueger, John Richard (1961), Chuvash Manual: Introduction, Grammar, Reader, and Vocabulary (Uralic and Altaic Series; 7), Indiana University, →ISBN, page 144