Clek strongly recommends that the Load Leg be used with all base installations, but there are some additional requirements surrounding when the load leg must be used:
For Children 10 kg (22 lb) or less:
The base can be installed with or without using the Load Leg. However, the load leg is an important safety feature of this car seat and using it is STRONGLY RECOMMENDED. If you are unable to install with the Load Leg, it is recommended that you install the base using the vehicle belt.
For Children over 10 kg (22 lb):
The base MUST be installed with the Load Leg. If you are unable to install with the Load Leg, you can install this car seat without the base.