Abstract :
This study aims to produce guided discovery based LAS on material that is valid and practical in class VIII flat-side room building MTs Masmur pekanbaru. The study was conducted on March 8-28 2019. The subjects of this study were VIII.1 MTs Masmur Pekanbaru students in the 2018/2019 academic year, which numbered 25 students with heterogeneous abilities. LAS is designed to consist of 4 meetings on cube and beam material. In this study follow the steps of R & D development research, namely potential and problems; data collection; product design; design validity; design revision; product trial; product revision; and the final product. The results of the study obtained an average validity of LAS of 80.20% with quite valid criteria. The results of LAS practicality were 80.7% with fairly practical criteria obtained from student response questionnaires. The results of the teacher's response to the use of LAS scored 87.5% with very practical criteria. Based on the results of the study it can be concluded that this development research produced a guided discovery-based learning device on cube and beam material in class VIII MTs which tested its feasibility (valid and practical).