Girder

The Girder is a utility. It is a long thin piece of metal platform that can be placed by the player. Once placed, the girder has no special properties over the rest of the terrain. It is usually used by players to make a piece of platform to prevent their worms from slipping into the water, but is most often used to protect the players'/enemies' worms from incoming threats.

Girder in the Wormopedia
"What planning permision?

''The Girder can serve many functions in the natural habitat of our wriggly chappies. The main use of the girder is to provide an excellent defence that will withstand one direct hit of the bazooka before leaving your Worms exposed. The Girder is also used in situations where a simple A to B gap needs to be bridged, just remember though that a well-aimed shotgun explosion at the foot of the Worm stood upon the girder will send him hurtling down below.''

''Sometimes you find yourself in a situation where you have a worm standing under an overhang at the edge of the landscape, so a grenade shot is definitely out of the question. If this happens, a well placed girder opposite your worm can act as a rebounding mechanism to impress even the most acquitted of Worms players. Remember though, the grenade may need to be set to high bounce and high fuse to travel the distance required."''

—Wormopedia's description on the utility.

First/Second generation games
Once the girder is selected, the girder's angle and length can be adjusted by pressing the Left and Right arrow keys. After 1 full turn, the girder will double in length. You can rotate the girder by pressing your jump button, bound to"Enter" from the start.

Third generation games
Once the girder is selected, the girder's angle can be adjusted by pressing the middle-mouse-button. Unlike first/second generation games, the girder can't increase in length.

3D games
Once the girder is selected, you can only move it, then place it. In the 3D versions of the game, length cannot be changed.

Tips & Tricks

 * You can use the girder to jump over a big gap.
 * Use the girder as a defence from weapons. Be careful, that some weapons can even pierce through girder(s) easily such as the Bunker Buster and the Blowtorch, dealing your worm some damage.
 * The Girder is usually limited, so spacing them out means you may not have to use as much of them, and since your worm can jump, you usually won't be at risk of falling if you are careful.

Trivia

 * In second generation worms, there is a glitch where you can put girders over anything, even worms. This was fixed in a beta update.