Additional uses for the Hide skill
D&D 3.5 rules from Complete Adventurer (p.101), partially reprinted later in Rules Compendium (p.92).
You can blend into a crowd, slip between areas of cover or concealment to maintain secrecy, sneak up on a foe, or tail a target.
Blend into a Crowd
You can use the Hide skill to blend into a crowd, but doing so conceals you only from someone scanning the area to find you. You remain visible to everyone around you, and if they happen to be hostile they’re likely to point you out.
Move between Cover
If you’re already hiding (thanks to cover or concealment) and you have at least 5 ranks in Hide, you can make a Hide check (with a penalty) to try to move across an area that does not offer cover or concealment without revealing yourself. For every 5 ranks in Hide you possess, you can move up to 5 feet between one hiding place and another. For every 5 feet of open space you must cross between hiding places, you take a –5 penalty on your Hide check. If you move at more than one-half your speed, you also take the normal penalty on Hide checks when moving quickly (–10 for moving faster than normal speed, or –5 for moving between half speed and normal speed).
You can also use this option to sneak up on someone from a hiding place. For every 5 feet of open space between you and the target, you take a –5 penalty on your Hide check. If your Hide check succeeds, your target doesn’t notice you until you attack or make some other attention-grabbing action. Such a target is treated as being flat-footed with respect to you.
For example, Lidda the 2nd-level rogue could attempt to dash across a 5-foot-wide doorway without revealing her presence to the orcs inside. Even though the open doorway provides no cover or concealment, she can attempt a Hide check as normal, opposed by the orcs’ Spot checks. She takes a –5 penalty on her check because of the distance involved. If she moved at more than half her speed, she would take an additional –5 or –10 penalty on the check depending on how fast she moved (see above).
You can try to follow someone while remaining unseen. If you stay at least 60 feet away from your quarry, you must succeed on a Hide check (opposed by your quarry’s Spot check) once every 10 minutes. At a distance of less than 60 feet, you must make a Hide check each round. Extraordinary actions on your part (such as spellcasting or attacking) may disrupt this attempt even if you do not fail a check.
Tailing someone still requires cover or concealment, as normal for attempting a Hide check. A moderately crowded street provides sufficient cover and concealment to accomplish this goal. Alternatively, you can duck between areas of cover or concealment, as described in Move between Cover (see above).
Even if you fail a Hide check while tailing someone or you are spotted while moving too great a distance between hiding places, you can attempt a Bluff check opposed by your quarry’s Sense Motive check to look innocuous. Success means your quarry sees you but doesn’t realize you’re tailing him; failure alerts him that you’re actually following. A modifier may apply to the Sense Motive check, depending on how suspicious your quarry is. The table below provides Sense Motive modifiers for particular situations.
Your Quarry is sure nobody is following –> Sense Motive DC –5
Has no reason to suspect anybody is following –> DC +0
Is worried about being followed –> DC +10
Is worried about being followed and knows you’re an enemy –> DC +20