Neil wrote:
My garage door spring needs retensioning as its reluctant to reach the fully
open position without the aid of a good shove. Replacement parts and
specialist tools to do the job are easily available online. I would
appreciate some pointers as to how its done - the prospect of the horizontal
spring unwinding whilst my fingers are in close proximity doesnt sound too
appealing. Many thanks

Dangerous. Get someone who has been trained to do it, or survived....

Googling "henderson Garage Door tension" will get some advice.

--
Adrian