Especially when processing thick leather qualities a relief-type seam pattern with hand made appearance is only made possible, if leather and thread thickness as well as stitch length and seam quality go well together. The heavy-weight long arm machines of class 221 are the specialists for this task offering ideal conditions due to the high clearance, the powerful and effective triple feed, the strong needle penetration power, the large stitch lengths and the oversized vertical hooks. When processing thick threads and heavy-weight materials the robust design and the excellent sewing kinematics allow a constantly tight stitch formation and consequently accurate seams as well as neat stitch pattern.