What do U-Joints look like?

Hi all,
I am getting a "clunking" noise that also jolts my '90 Jeep Cherokee (Pioneer) backwards when I hit the gas pedal. I started getting this problem after I added a 2" lift (blocks).

I've had some people tell me that this may be my u-joints.

What are u-joints and what do they look like? Are there any pictures on the web?

Thanks.

Look at the end of you drive shaft and you'll see one of those.

http://www.jeepin.com/features/ujoint/index.asp

http://www.stu-offroad.com/misc/u-joint-1.htm

Sounds like the blocks are adding axle wrap into your problems, and I'd recommend greasing the slip splines on the driveshaft...they'll make a 'clunk' when dry. Some of the 'clunking' problems are also attributed to the rear brakes being out of adjustment and holding tension in the driveline - when you let off the brakes and hit the gas you feel the tension released as a 'clunk'

Hey Yucca Man,
I think your comment sums up what I am experiencing.

I noticed that when I put the Jeep in Neutral, I can move the driveshaft a bit, but when the Jeep is in Park gear, I can't move it. Is this one way of looking for the problem? I heard that it is not supposed to have any "play" at all.