Short answer: order the box blank and put the security in the cover hardware. A custom stainless junction box at 4 x 4 x 2-1/8 in [102 x 102 x 54 mm] with zero cutouts is a straightforward custom build: the body is built from one piece, the lid closes on a gasket, and delivery is 10 business days from your approval of the drawing. Two facts shape the decision. A knockout is a scored disc that is meant to come out, so a blank wall removes the easiest opening in the box. The cover, not the wall, is where a box actually opens, so tamper-resistant screws do the real security work. Order Type 1 for a dry indoor room and Type 4X / IP66 for washdown or outdoors; ratings are manufacturer ratings, not UL listed.
What a knockout means for security
A knockout is a disc stamped into the wall of a box and scored so one strike knocks it free. The scoring is deliberate: the day a cable enters, the disc has to go. UL 50 Table 71-1A lists the knockout diameters and fitting dimensions for boxes, and the common 1/2 in trade-size knockout cuts a hole about 7/8 in [22 mm] across. On a standard catalog box those discs sit on the sides, the back and the ends. Each one is a ready-made opening sized for a probe or a hand-started fastener. A blank body ends all of that: nothing scored, nothing dimpled, and nothing that leaves with one blow, so the wall resists the same everywhere.
The catalog route does exist. Drawn steel blanks, pressed from one sheet with no punched knockouts, are listed in the 4 in square by 2-1/8 in deep trade size, the drawn body suits surface mounting, and the sides accept field punching if a cable shows up later. Hunting those blanks across distributors is the slow part. We build the same idea at your size in 304 or 316L stainless, from one piece, minimum quantity one; the catalog-vs-custom buying guide lays out when each route wins.
Which rating the location needs
A secure indoor room, dry and wiped with a cloth, needs only Type 1: the indoor general-purpose type that keeps out fingers and falling dust. Washdown, rain or hose-directed water moves you to Type 4, and corrosion resistance adds the X, which is Type 4X in 304 or 316L stainless, built as a custom enclosure at your size. If the specification is written in IP language, order the NEMA type anyway. NEC 110.28 states that IP ratings are not a substitute for enclosure type ratings, so a Type 4X line satisfies both at once. The NEMA enclosure types guide walks through what each type stands for.
A UL listed enclosure has been evaluated by UL to UL 50E; where the installation demands listing, the listing comes with the product, not the drawing. A blank body keeps the rest simple: with zero openings in the walls, the rating rests on the door gasket and the cover fasteners, which is the hardware you are specifying anyway.
Material: drawn steel, 304 or 316L
A dry indoor room with no corrosion: a galvanized drawn steel blank does the job and keeps the weight down. Painted carbon steel adds one chore. NEC 250.12 requires paint, lacquer and enamel removed from threads and contact surfaces where grounding and bonding connections land, so the ground lug meets bare metal. Stainless skips that step, because the lug lands on clean metal. Where the box gets washed, 304 is the indoor washdown and general outdoor grade. 316L is the grade for salt air, brine, chlorides and chemical areas. Both run through the custom enclosure builder at whatever width, height and depth you draw, with #4 brushed as the standard stainless finish.
What fits inside the 4 x 4 x 2-1/8 in blank box
- Body from the required footprint: 4 in x 4 in x 2-1/8 in [102 x 102 x 54 mm].
- Usable volume marked on a box of this trade size: 30.3 cu in [497 cm³] (NEC box-fill volumes; manufacturers stamp it on the box).
- Allowance per conductor, from the NEC box-fill table: 2.0 cu in for each 14 AWG conductor, 2.25 cu in for each 12 AWG conductor.
The outer envelope is larger than the usable volume: 4 x 4 x 2.125 = 34.0 cu in [557 cm³]. Walls, drawn corners and internal fittings take the difference, which is why the marked 30.3 cu in is the number to divide by. The rule: conductor count = marked volume / allowance per conductor.
30.3 / 2.25 = 13.5, so 13 conductors of 12 AWG.
30.3 / 2.0 = 15.2, so 15 conductors of 14 AWG.
A blank box at this trade size therefore carries a 13-conductor 12 AWG splice with a conductor or two in hand. Past that, step up to the 4-11/16 in square, 2-1/8 in deep trade size, marked 42.0 cu in [688 cm³]: 42.0 / 2.25 = 18.7, so 18 conductors of 12 AWG. A switch or receptacle takes its own allowance out of the same total, so count the device before you count the wire. The full fill method, glands included, sits in the guide to sizing a junction box without conduit.
Entries, mounting and the cover that opens
Put every cable entry on the drawing as a factory cutout, with gland size, thread and position. Field-cut holes in a finished wall are the slow and leak-prone path. The choosing factory cutouts for repeat work article shows how planned positions pay off across a production run.
Mount through the back with the fastener heads landing inside the box. The wall screws then sit behind the cover and come out only after the tamper screws do. Outdoors, seal those through-wall screws the way the mounting screws through an outdoor enclosure article describes, or water follows the threads in.
The cover is where the box opens, so close it with hardware that fights a common driver:
- Pin-in-hex and pin-in-Torx screws need keyed drivers: the everyday panel choice.
- Spanner screws take a two-prong key and suit covers the public can reach.
- One-way screws install with a standard driver and refuse to back out: use them for permanent mounts.
Match the screw material to the body, so stainless screws in a stainless box. The fasteners for a gasketed access panel article covers the screw-and-gasket pairing, and a silicone lid gasket spans about -60 to 200 C, so temperature never picks this fight in a dry room. For the drive types side by side, the tamper-resistant screw selection guide for industrial enclosures compares them by tool and by use.
If the area is classified
A fuel bay, a hangar or any area classed for flammable vapor needs a junction box designed for that location: NEMA 7 or 9, explosion-proof construction, carrying the approval the area demands. We do not build hazardous-location enclosures, and a Type 4X blank body is not a stand-in for one. The Class I Division 2 junction box article explains when ordinary Type 4 terminals are allowed to stay in service. The two habits from this article still carry over to the classified-rated box: no removable discs in the wall, and cover fasteners a common driver cannot back out.
What to put on the order
Decide the material from the environment, hold the walls at zero openings, and spend the security budget on the cover. Torn between modifying a standard body and going fully custom? The custom stainless cutouts page compares both paths.
| Order line | What to write |
|---|---|
| Size | 4 x 4 x 2-1/8 in [102 x 102 x 54 mm], or your measured footprint |
| Material | 316L stainless, #4 brushed (304 where chlorides stay away) |
| Cutouts | None: zero openings in the walls, back and ends |
| Rating | Type 4X / IP66 for washdown or outdoors; Type 1 for a dry indoor room |
| Cover | Gasketed lid, closed with tamper-resistant stainless screws |
| Entries | Any gland or hub as a factory cutout on the drawing |
| Quantity | From one piece |
| Delivery | 10 business days from your approval of the drawing |
Send a hand sketch when there is no CAD. The what to send for a quote without CAD article lists the dimensions and cutout details that turn it into a drawing to approve.
Catalog dimensions to compare
Compare these catalog dimensions with your component layout. Open each enclosure for its rating, material and usable space, then check those specifications against your application.
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 6 × 6 × 4 in | 304 stainless | 6 x 6 x 4 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 8 × 6 × 4 in | 304 stainless | 8 x 6 x 4 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 10 × 8 × 4 in | 304 stainless | 10 x 8 x 4 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 12 × 10 × 6 in | 304 stainless | 12 x 10 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Do manufacturers make junction boxes with no knockouts?
Yes. Drawn steel blanks, pressed from one sheet with no punched knockouts, are listed in catalogs in common trade sizes, including 4 in square by 2-1/8 in deep, and the drawn design suits surface mounting. For anything beyond that, order a custom body: we build 304 and 316L stainless boxes at your size with zero cutouts, from one piece, minimum quantity one.
Does a blank wall actually make a box harder to break into?
At the wall, yes. A knockout is a disc scored so one strike frees it, and the common 1/2 in trade-size knockout leaves a hole about 7/8 in [22 mm] across. A blank wall gives nothing to strike out and no hole to pass anything through. The cover remains the practical entry, so tamper-resistant cover screws deliver the bigger security gain.
Does a blank wall also help the weather rating?
Indirectly, yes. The manufacturer rates the drawn body Type 4X / IP66, and the weakest opening sets the rating of the finished assembly. Zero cutouts means zero penetrations to seal, so the rating rests on the gasketed cover and its fasteners alone. Any opening added later has to carry a sealed, rated gland to hold the same level.
Which stainless grade suits a coastal or chemical site?
316L. Its molybdenum raises pitting and crevice resistance in salt air and brine, which is exactly what a coastal wall box sees. Watch surface temperature too: from about 60 C (140 F) up, chloride stress-corrosion cracking becomes a risk for 304 and 316L alike, so a box mounted near a heat source deserves a placement check as well as the better grade.
What if the secure area is a classified location?
Then the box itself must carry the hazardous-location design: NEMA 7 or 9, explosion-proof construction, with the approval that the classed area demands. We do not build hazardous-location enclosures, so source that box as approved equipment for the area. The blank-wall and tamper-screw logic still applies afterwards: no removable discs, and cover fasteners a common driver cannot back out.
