The girdle of Brahmana should be made of Munja grass. That of a Kshatriya should be a bowstring. The Vaishya's girdle should be made of the Valvaji grass. This has been laid down in the scriptures.
विप्रस्य रशना मौजी मौर्वी राजन्यगामिनी। बाल्वजी ह्येव वैश्यस्य धर्म एष युधिष्ठिर।॥