What's inside
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What the reveal means
A door jamb reveal is the visible gap between the edge of the door and the inside edge of the jamb or stop. On a fitted door, that gap should be even enough that the door opens freely and looks deliberate. The exact target depends on the door, hinges, stop and finish; a common starting point for an interior door is about 1/8 inch along the sides and top. Treat that as a reference, not a rule for every opening.
A steel rule is useful for checking short, narrow gaps because its graduations are fine and its edge can sit close to the jamb. It is not a substitute for checking the door in the position where it will actually hang. A door can show a good reveal while open but bind when closed if the jamb is twisted, the hinges are loose or the stop is set poorly.
Tools and preparation
Use a clean steel rule with clear graduations, ideally marked in 1/32-inch increments. A 6-inch rule is easier to position in a tight corner; a 12-inch rule gives more reach. A rule marked only in 1/16-inch increments is adequate for rough checks, but it makes small variations harder to distinguish. If you do not already own one, a 6-inch steel rule with 1/32-inch graduations is a practical size for door work.
Have a pencil, a small flashlight and a notepad ready. Before measuring, close the door gently and confirm that the latch, hinges and stop are not forcing it out of position. Remove grit, paint flakes or debris from the gap. Do not measure over a thick coat of wet paint or put pressure on the door that changes the gap.
Check that the rule’s zero end is intact. A chipped, rounded or bent end can introduce error when you use it as a reference. On a rule whose first graduation is not exactly at the end, start from a visible mark and subtract that offset rather than assuming the end is zero.
Measure the reveal
Close the door until it rests normally against the stop, without pushing it hard. Hold the steel rule perpendicular to the door edge and jamb, with its flat face visible. Place the end near the gap and read the distance from the door edge to the jamb edge. Keep the rule out of the hinge barrel and do not wedge it between the door and stop; forcing it in can move the door or damage the finish.
Take readings at several points instead of relying on one. For each side, measure near the top, around the middle and near the bottom. Check the top reveal near both corners and at the center. Record the numbers, such as “hinge side: 1/8, 5/32, 1/8 inch.” That pattern is more useful than writing “looks uneven.” A difference of 1/32 inch may be difficult to see and may be acceptable; a change from 1/8 inch to 1/4 inch is usually worth investigating.
If the rule is too wide to fit or blocks your view, use it as a scale rather than inserting it into the gap. Hold its edge beside the reveal and sight square-on. Looking from an angle creates parallax: the apparent gap shifts as your viewpoint moves. A narrow card or feeler gauge can help check a tight gap, but a steel rule is better for reading and recording larger reveals accurately.
Read the pattern, not just the numbers
Compare the measurements across each edge. A nearly constant gap suggests that the door and jamb are aligned in that direction. A gap that widens steadily from top to bottom may indicate a jamb that is out of plumb, a door that is out of square, or hinge positioning that needs attention. A narrow spot near a hinge can point to a loose screw, a hinge leaf sitting proud, or a jamb that has moved.
Check both the latch side and hinge side. Do not assume the door should be centered in the opening: the hinge side often needs to be set first, and the latch-side reveal is adjusted to suit the door’s swing and latch. Also inspect the top corners. A door that touches at one upper corner may be racked even if the side gaps look acceptable at mid-height.
When the door is open, note whether it stays put or swings by itself. That is a separate check for jamb plumb and hinge alignment; the reveal reading alone cannot diagnose it. If you find a substantial or changing gap, check the hinges, frame and door before removing material from the door edge. Planing the wrong edge can make the reveal worse or leave too little clearance after seasonal movement.
Choosing a measuring tool
| Tool | Best use | Trade-off |
|---|---|---|
| Steel rule | Reading and recording a short gap at several points | Needs a square viewing angle; a short rule may not reach far |
| Feeler gauge | Comparing a very narrow gap or checking contact | Leaves a less convenient numeric reading if you need to record varied widths |
| Combination square | Checking a gap or carrying a reference from one location to another | Bulkier in a tight reveal; its blade can obscure the edge |
| Tape measure | Checking the overall door and opening dimensions | Awkward for reading a small reveal precisely |
For occasional household work, an inexpensive rule is fine if the markings are legible and the edge is straight. Paying more for a hardened or corrosion-resistant rule mainly makes sense for frequent site use, where tools take knocks and get handled with dusty or damp hands. If you need to measure repeated narrow gaps rather than record dimensions, a set of inch feeler gauges can complement a rule. Neither tool corrects a misaligned door.
Common mistakes to avoid
Do not measure with the door partly open: the gap changes with the angle, and the result cannot be compared reliably with the closed-door reveal. Do not press the door toward the stop while taking readings. That can hide hinge play or make a loose door look better than it is. Likewise, do not compare measurements taken with the latch engaged to ones taken with the latch retracted if the latch pulls the door into a different position.
Another common error is measuring from the wrong edges. Be consistent: measure from the door edge to the jamb edge, not from the door face to the stop, unless you are specifically checking stop clearance. If the jamb is painted, use the finished surfaces as they are; the door must operate against the actual finish, not an imagined bare-wood opening.
Finally, record the readings before making adjustments. A simple list of six or eight measurements gives you a baseline and shows whether a change helped. If the reveal varies widely, the door rubs, or the frame moves when the door closes, correct the underlying fit first. A steel rule tells you where the gap changes; it does not tell you which component is at fault on its own.