The TP-Link RE700X can be used to extend your WiFi network to an outdoor garage, but there are a few important considerations to take into account:

1. Range and Obstacles: The RE700X is designed to extend the range of WiFi in homes, but range can be affected by physical obstacles such as walls and doors. Make sure the signal from the main router is strong enough to reach the repeater.

2. Access Point Mode: The RE700X can be set to Access Point mode if you have an Ethernet connection available in the garage. This turns a wired connection into a WiFi access point, which could be useful if you have an Ethernet connection in the garage.

3. Climatic conditions: Since the garage is outdoors, make sure that the repeater is placed in a location that is protected from bad weather and extreme climatic conditions, as it is not designed for outdoor use.

In summary, the TP-Link RE700X can be used to create a WiFi hotspot in an outdoor garage, but it is crucial to check the signal strength and consider the conditions of use.