Once the economic outlook improved, Onni K. Rentto, now a Master of Science in Engineering, started to look for a shoe manufacturing company to buy, eventually finding one in Hyvinkää. In 1938, he became the director of a company that continued operating until 1990.
A decade earlier, Rentto Oy had bought a majority holding in Aaltonen’s shoe business. After this transaction, Aaltosen Kenkätehdas Oy (Aaltonen Shoe Factory) was founded. The factory ran until 1997.
In 1953, Onni K. Rentto brought from Germany the idea of manufacturing cellular rubber. In the same year, the company leased the premises of Hyvinkään Saha Oy (Hyvinkää Sawmill) at Sahanmäki in Hyvinkää. This is where the rubber industry of Rentto Oy began.