This is probably an old idea but everyone I have mentioned it to laughed at me
We took a friend trampoline away due to moving,it is rusty and delapidated,however,we came up with using the springs on our gates,and it works!
Well,most do,the small one at the bottom closes like Arkwrights till!
Here is a picture of one, on one of the chicken runs.
p.s. I have several hundred of these springs available which are old,a bit rusty but all work well,let me know if any would be suitable-it's great on gates for the chicken runs and allotment gates-to keep my girls out!!