Kennel/Pen Building- Joining panels?

Trying to join the top and bottom 2"x4"x8ft L rails of both my panels end to end like the drawing below shows...

Does anyone have a good idea how this can be done effectively?

I was suggested to use connection plates and screw on both sides...

Another suggestion was to place another 4 ft l 2x4 over both sides and nail them together.

any help?

 

Attach a cheater block under the top plate on left side. Basically center a 2'L 2x4 under left, leaving 12" run wild, to attach to bottom of the right pannel.

 

Frame it like a stud wall, simple and effective

 

2x4 is how I do it.

 

If it's gonna be a permanent structure. When you pour your foundation use J bolts.

 

I hope to keep it as a modular set up...the ground will be concrete if that makes any difference and I would prefer not to drill into the concrete if possible...