String Can't Connect to Wire

I was trying to make some traps so I got out some string and a tripwire. I put the tripwire on a diamond block and put the string next to the tripwire. But it did not connect. Even when I added the other tripwire and string which also did not connect. I walked over to see if it still works but no. I even checked to see if it gave of a Redstone signal. Still no. Please help.