Since the Mamluk sovereign al-Zahir Baybers (d. 1277) appointed four chief judges in Cairo representing the four Sunni schools of law, the different schools achieved a high level of independence, opening the doors for litigants and the legal establishment to utilize this system for utilitarian purposes. One technical term associated with the utilitarian use of the diversity of legal schools is talfiq, which is the putting together of two elements of different schools to create a new complex doctrine. I will first argue that contrary to common wisdom in the field, talfiq was used in the courts of the 17th and 18th centuries, i.e. prior to its use in 19th-century legal reforms in Egypt. Through the survey of 1001 cases from the Ottoman Egyptian courts of al-Bab al-'Ali, Misr al-Qadima and Bulaq, I show that families from different social strata used talfiq to facilitate their legal transactions, especially in cases of divorce, marriage and waqf (religious endowments). Sometimes more than one school was used in the same case to avoid a final dissolution of marriage. The Egyptian Ottoman court records also provide many examples of great jurists attending the legal process, observing those cases of talfiq, suggesting that legal theorists accepted this court practice in the eighteenth century. In the second part of the study, I engage the theoretical legal literature (usul al-fiqh) to explore the legal status of talfiq. I have found that not only did jurists' attitudes towards talfiq grow more permissive in the 17th and 18th centuries, that they also considered people's practice in the courts as a justification for the permission of talfiq in legal theory. I conclude that talfiq is not a modern innovation that was opportunistically employed by 19th century legal reformers to accommodate modernity as some scholars have argued, but it was part of the legal culture of the Ottoman period. I also argue that Islamic legal theory did not stand in opposition to social practice, but responded to, as well as shaped legal practice. Just as court cases cite the theoretical legal literature, legal theory in the Ottoman period referred to common practices.