C型槽口的五金设计原理符合铝合金门窗的要求
The hardware design principle of C slot is in accordance with the requirements of aluminum alloy doors and windows
U型槽口在欧洲是针对塑料门窗和木门窗的专用五金槽口，采用自攻螺钉螺接的方式安装五金件。
U slot in Europe is a special hardware slot for plastic doors and windows and door windows, and the hardware is installed by the way of self - tapping screw.
但是当应用在铝合金门窗上，安装U槽五金用的自攻螺钉要承载由门窗开关所产生的纵向剪切力，由于自攻螺钉的硬度远远大于铝合金型材，自攻螺钉的螺扣就会对铝合金型材产生破坏，造成安装孔扩大，长此以往五金件的螺钉连接就会出现脱扣。
But when used in Aluminum Alloy windows, installation screws U slot hardware to bearing longitudinal shear force generated by the switch, the tapping screw hardness is far greater than the Aluminum Alloy profiles, self tapping screw thread will cause damage to the Aluminum Alloy profile, resulting in a mounting hole expansion screw hardware if things go on like this the connection will appear tripping.
而塑钢门窗的内衬为钢材，材料硬度与自攻螺钉相当，不会发生安装孔扩大和五金件脱扣的现象。
The inner lining of the plastic steel doors and windows is steel. The hardness of the material is equal to the self tapping screw, and the expansion of the installation holes and the release of the hardware will not occur.
由于U型槽口应用在铝合金门窗上不符合机械设计中的机械材料等强设计原理，出于对门窗五金安全性的考虑，欧洲铝合金门窗不采用U型槽口五金。
Because the application of U notch on aluminum alloy doors and windows does not conform to the strong design principle of mechanical materials in mechanical design, because of the safety considerations for doors and windows, the U type slot hardware is not adopted for European aluminum doors and windows.