Agree with Rowan, although Jack Russell's can jump quite high. Mine ran up an almost vertical cliff like a mountain goat!! And also agree they can dig under it if it's just erected on grass or soil. Many are the times when mine was young that she did just that!!
Years ago, my lovely JRT boy had a darn good try, leaping up and clinging on and attempting to clamber the rest of the way over. Why such an effort? There was a gorgeous Standard Poodle in heat on the other side. He gave up and started to dig underneath so I had to bring him in. He was a game lad though but it was a bit too much and I don't ever think one would get clean over it. But under it is a different story.
Without any shadow of a doubt YES my Freddie does it daily (my bitch can't,) but Fred a parsons JTT can do it with only a shor run up!!!!!! little bu**ger
Err B00, "clear completely" doesn't sound the same as "not so much jumped, as climbed up a brick wall." Well not to me anyway. X
Just have to say JRTs are the most brilliant dogs, great fun and never a dull moment and right little characters.
Had a JR cross who was a superb scrambler in The Lake District and Snowdonia.
The only time he put a foot wrong was on Sharp Edge, Blencathra, where he used somebody's head as an extra pawhold.
I doubt if ANY dog can clear a 6ft fence without touching it.
Our opposite neighbour has a JR that will scramble over a 6' picket fence, using the rails as support. It easily gets over to greet other family members.