Corner braces and flat straps from tool station on the inside of the sleepers did a good job recently.
I had two in each corner (per sleeper) and flat straps to join the two levels.
I use these, quick and easy to drive in with an 18v drill, seem very strong.
I use Spax Wirox screws which are a high performance star drive screw. These shown below were predrilled but then they are oak sleepers, with pine sleepers I have used them straight through without any problem. Never had a problem with these snapping either upon installation or up to 2 years after.
I would say though that the fixing you choose should reflect the loading you are expecting the sleepers to hold back so if its for a wall or terracing then the rebar mentioned above would be a better option, altho the manufacturers of the screws would probably disagree
They are available most places but screwfix sell them here:
I too use timberloks, you need an impact driver to get them in though without piloting. I was in a local merchant about 2 years ago and they had the 175mm ones in boxes of 500 for 45 quid. Needless to say i bought about 6 boxes so am stocked up for another year or two yet.
Thanks guys that has really given me food for thought! Prob go fro the special screws!
On the same discussion do you use a chop saw to cut the sleepers (I will be using new sleepers) Have used my chainsaw in the past but the cut was a bit too rough for my liking.
timber locks are top screwws I fired some into 450 sq green oak cubes as small feet and left then out for a year,when I took then out they were as new .
when i made my sleeper beds at home I drilled them and used 10.mm stainless bar too hold them together
I use the chainsaw for all plumb cuts. For the mitres i tidy them up with a circular saw. Sleepers are a bit un-weildy for a chop saw.
I ended up using timber locks. Very strong and went in very easy with my makkita impact driver.
Cost me arround £0.60 each, well worth it to be honest!
Thankyou all for helping me with my dilema. much appreciated.
Will add some pics of what i achived!