As with the iPhone, the number one reason for removing the digitizer is if it’s smashed. Removing the broken glass from the mid-frame is a delicate procedure and can be very tedious and time consuming. The rubber gasket and home button can be easily damaged if you are overzealous with a heat gun. The mid-frame section is now readily available as an orderable spare part (about £5!) and in my opinion you’ll get a much neater, cleaner repair if you replace this part too. There is however no need to purchase a new home button and switch as this can be easily removed from the old mid-frame and applied to the new one, you will need a hot iron to melt the plastic rivets that hold it in place though.

The number one reason for removing the digitizer and LCD assembly is if the digitizer is smashed. Removing the broken glass from the mid frame is a delicate procedure and can be very tedious and time consuming. The rubber gasket and home button can be easily damaged if you are overzealous with a heat gun. The mid-frame section is now readily available as an orderable spare part and in my opinion you’ll get a much neater, cleaner repair if you replace this part too.

yosarianからの引用：

When reassembling the display and bezel, how should one install the gasket? What happens if the gasket is damaged while the phone is being disassembled? Is there a replacement or some other fix?