Use Magic Device

Use Magic Device (Cha)
The Use Magic Device skill is a class skill for Bards and Rogues, and a cross-class skill for all others. It is a trained only skill, meaning its use can not be attempted without training at least one rank.

In DDO the Use Magic Device skill is used to allow a character to use a wand or scroll without the usual requirement of having the stored spell on said character's spell list. Wands and scrolls that contain a spell already on a character's spell list can be used without fail or skill check as long as the minimum level requirement is met.

Attempting to read a scroll or activate a wand that contains a spell not on a character's spell list triggers a Use Magic Device skill check against the DC of the scroll/wand. The DC of a scroll/wand is 18 plus two times the minimum usage level of the item. A succesful skill check uses up the scroll or a single charge from the wand and unleashes the stored spell effect. A failed check also uses up the scroll or wand charge, but there is no spell effect released.

The DC for wands is 18+(2*Caster Level)

Some example DCs:  

Note that the (6th) in the Wand of Lightning example denotes a higher than normal caster level for the wand. Lightning Bolt is a 3rd level (5th caster level) spell.

Additional uses: Some items are restricted to a specific race, class, or alignment. Examine these items to see if they have a listed difficulty. If so, you can use that item even if you do not fit the required criteria by having a Use Magic Device skill greater than or equal to the difficulty level of the item. This applies most notably for weapons and armor, which will generally have more powerful attributes in exchange for class or race restrictions. Use this skill to bypass those restrictions. Note that items that are restricted by an "absolute" clause (i.e. "Race absolutely required:" or "Race absolutely excluded:") will never be usable by characters excluded by such a criterion. These items will not have listed difficulties.

Note that bypassing race or alignment requirement does not get a roll to add to your UMD modifier. It is a simple comparison between the item's Difficulty rating and your UMD modifier. You can, however, buff yourself (Eagle's Splendor, Rogue's Action Boost, etc) to get high enough. You only must maintain the UMD long enough to equip the item, and then you can use it continuously after that (until log-out, at least). Thus, buffing UMD to bypass a restriction is more useful for armor or worn items than for weapons, which need to be switched around frequently.

To use an item of another alignment requires a 20 UMD (for examples, see the Iron Manacles from Delera' Tomb bracers or Retribution from Threnal). Generally a race restriction will reduce the weapons level requirement by 2 levels, and the difficulty for race restricted items is 10 + the modified level. Therefore, an armor that would normally require a level of 10 would be level 8 and have a difficulty of 18.

Additionally, an item that has an alignment and a race restriction will generally only use the race restriction's difficulty rating. This means that a +1 Icy Burst Light Hammer of Pure Good (Dwarf Only, Minimum Level of 4) should have a 20 difficulty from the Pure Good modifier and a 14 from the Dwarf only modifier, but only the 14 difficulty is actually present.