Flags Yard

What is a sure fire way to train your dog to stay in your yard?

I know its my fault. My dogs are 5 now, and ive had them since they were 10 weeks. They are pure German shepherds. The are very friendly, well socialized, but their prey drive is strong. Basicly, they will stay in the yard, but everytime a neighbors dog comes out, zip and their off. I suppose i first need to teach them their boundries, can i do that with cones or flags, second use a 12 foot training leash and pull them back if they go beyond the boundry, or what ? Help!!!!!!!!!!!111

You are correct-you need to teach them their boundaries.It’s one of the first things they should have learned as pups.
Flags and cones are’nt necessary.But can be used if you want.Just put a long leash on them and follow them around the yard giving a quick jerk and a harsh NO when the get too close to the boundary line.
Gsds need lots of exercise.Leaving them alone in the yard to entertain themselves won’t do at all.They need a good 5 mile run everyday to wear them out.You also need to give them a job to do.
You’ve not given them a job,so they found one for themselves.
I have 2 as well.I put them outside and they sit and look in the door until I let them back in.As long as no one tries to come onto the property they will not leave the yard evan to chase after bunnies,cats or squirrels.
I keep mine quite active.They like to make their own choices and solve problems and keep me on track.There’s little deviation from the routine I have established for them and they let me know when it’s past time for something to happen that involves them daily.

Fallen Flags: D&H arrives at Pot Yard