I know, Devonlady. I have a feeling it's going to be cable ties, but I'd love to know how I SHOULD have done it!
I purchased a simple hand held non commercial use spot welder from Machine Mart 25 years ago for less than £ 150 ( I did say 25 years ago !
)
I've just checked MM & found ...Clarke CSW13T Spot Welder (with timer) it's nearly £500 these days
( Still very good value if you have the work for them )
I made well over 1,000 small cages and the same number of drinker attaching plates and full four foot diameter lid reinforcing strips with bit each set up needing 53 welds . Plus zillions of other thin steel /thin galv /stainless steel , copper or brass things .
You never know how useful one is on a small holding/small farm till you're without one after having had one for 20 odd years ( I sold up when I became disabled for the second time).
Perhaps try and see if you can hire a hand held spot welder .
From the likes of HSS or any decent small plant/equipment hire company.
Some spot welders will spot weld up to 6.4 mm ( 1/4 inch ) wires on to 4 mm metal without any difficulty .
The big water cooled continuous use commercial ones can spot weld 10 or more mm of steel etc.
Before you do hire one make sure you have all manner of thin steel things ready such as dog guard for the car /truck , dog crates , different mesh garden /farm sieves /riddles , brackets & boxes etc . for a single days spot welding session .
This way you can work 24 hrs solid if needs be
. That way you get the best value for your money.
Hiring a small tig or mig machine with a reasonable gas bottle is also an option but only if you know how to tig /mig weld for it can be expensive , even with the no gas fillers /wires set ups. .
Failing that drill the angle irons and fit large " penny washers on the inside of the angle iron with small fully threaded bolts that are using , " nyloc " nuts. Fitted so that the penny washer traps the mesh under the washer & between the internal edge of the angle iron so it won't come free . Nor will the Nyloc nut come free & be eaten by the animals unlike normal nuts 7 spring washer if they are slightly disturbed .. This usually entails you putting a bolt through at the inside edge of two opposite wires of a square so it can't slip /slide free . Put one in each corner as well to trap the corner securely . You can always cut a penny washer down to size with a hacksaw to get a good corner or fit along a length .
You could also use extra long big headed pip rivets if you can get hold of or hire a decent long armed tongs type riveter. Big rivets in 6 mm diameter or so shanks at 15 to 20 mm long with 18 mm or so cheese / pan or flat head are not too expensive on eBay
As said use basic " Tec screws " + washer and metal strips , either insert them in pre drilled pilot holes using suitable power tools or a specialist slow speed geared down torque settable Tec screw gun in un drilled metal over 3 mm or so if using self tapping / screw thread cutting high tensile Tec screws ..
The Tec screws can be expensive , if you can only buy them by the box of 200 or so but you soon find all manner & excuses to use them , especially the ones with a rubber sealing gasket under the head washer .