Purpose – This paper seeks to analyse the internal materials flow in lean manufacturing in an assembly line of the Bosch factory, located in Spain. The objective is to develop a handling system in a small space, capable of solving the problems of accumulated intermediate stocks of parts. An improvement is proposed adopting the milkrun handling system, while verifying the advances by means of lean metrics. Design/methodology/approach – Based on this case study, the paper identifies data from value stream mapping and uses lean metrics, such as dock-to-dock time and lean rate. The case study develops a timetable and routing analysis for the milkrun to improve materials flow. Findings – The proposed logistics allows an improvement of lean metrics, without modifying the layout and production planning. The routing flexibility of the milkrun reduced stocks, work-in-process and dock-to-dock time, while increasing lean rate. Research limitations/implications – The findings are limited due to the focused nature of the case study. Although the solution is designed for a particular plant, the methodology is fully exportable. Practical implications – The paper shows a real case study illustrative for systems management. This research shows significant benefit associated with the implementation of lean programs. Originality/value – It details how the application of lean manufacturing tools could necessitate a study of materials handling to improve lean metrics.