How do manufacturers engineer their aircraft to deal with tail strikes?
During testing, the rear fuselage is protected by a beam made of oak or even steel to distribute the tail strike loads and to protect the aircraft skin.

A340 during tail strike tests. This one is literally blazing along the runway …

For normal operations, the protection is removed. However, tail strikes must not cause flight-critical damage, so a few precautions are taken during design:


No hydraulic or electrical lines must run along the bottom of the rear fuselage.
If there are still mechanical control elements like pushrods, they and their collapsing supports must not be close to the bottom of the fuselage.
The tail strike location must be outside of the pressurized part of the fuselage.


The main protection against tail strikes, however, is procedural: The rotation speed must be high enough to allow lift-off before a critical pitch attitude is reached.

Delta wing aircraft are much easier to over-rotate, so the Concorde used a retractable tailwheel for tail strike protection: