2 moving leaf and 2 fixed panel
1. to achieve shifting the opening sash 7mm to the frame during locking sash procedure, ensuring high sealing level.
2. The connecting structure between opening sash and the running wheels is a set of bearing, decreasing friction force during shifting the sash to the locked position.
3. Doule wheels structure of the roller carriage makes the sash sliding very smoothly, and prevents digression under strong wind load.
4. Roller carriage should be installed after all transmission components have been properly adjusted, overcoming allowance caused by connection among transimission parts and link rods.