Where to place a Marker

Height is the first decision

An NFC tap needs contact, or close to it. That means the Marker has to be somewhere a person can comfortably put a phone, not merely somewhere they can see.

Surfaces that work

Painted drywall, plaster, wood, laminate

The easy cases. Clean, flat and non-conductive. Nothing to think about.

Glass and acrylic

Radio passes through both, so a Marker on the outside of a tank surround or a display case reads normally. Clean the surface properly first: glass is the surface adhesive most often fails on, and it fails days later, not immediately.

Stone, brick, ceramic, fabric

All fine electrically. The problem is texture: a rigid three inch Marker needs its whole back in contact, so a grout line, a rough face or upholstery wants a plate or a holder rather than bare adhesive.

The three cases that cause trouble

Metal

Metal directly behind an NFC antenna detunes it, and a tap that worked on the bench stops working on the panel. We do not publish an on-metal rating for the Marker, so treat metal as the case you test before you commit: hold the Marker against the actual spot and tap it with two phones. If it is unreliable, lift the Marker off the metal on a rigid non-metallic spacer or move it to the nearest non-metal surface. The printed QR is unaffected, which is a good reason to keep the code on a face that has to live on metal.

Curves

A three inch Marker is rigid. It sits happily on the flat cap of a habitat rail or the top of a wide post, and badly on anything with a tight radius: a handrail, a stanchion, a pipe. If the surface curves noticeably across three inches, mount to a flat plate and fix the plate instead.

Outdoors

The Marker is UV-resistant and rated for outdoor mounting. The failure outdoors is almost never the Marker: it is the adhesive, which lets go through freeze-thaw cycles and on surfaces that were damp when it went on. Prefer a mechanical fixing, mount under an overhang where you can, and avoid anywhere water runs across the face.

Five placements that work

• Cedar Hollow Zoo & Aquarium: on the flat cap of the habitat rail at the otter viewing window, about 40 inches up, where visitors already rest a hand. Above the splash line, below the sightline into the enclosure.
• Ridgewood Museum of Natural History: beside the exhibit label at 50 inches, aligned to the label's right edge, on the same wall rather than on the case glass so that cleaning crews never have to work around it.
• The Bellhaven Hotel: flat on the bedside table beside the lamp, where a guest is already putting a phone down. A horizontal surface at 28 inches gets tapped far more than a vertical one behind the headboard.
• Marigold & Vine: on the vertical face of the table edge nearest the aisle, not on the tabletop, so it survives wiping down and does not sit under a plate.
• Harbour Point Aquarium: on the sloped shelf of the tank surround, below the acrylic, angled up. Acrylic is no obstacle to a tap, and the shelf is the one place at a tank a visitor can rest a phone without leaning over the water.

Things to avoid

• Behind glass a visitor cannot touch. A Marker in a sealed case is unreachable by NFC, and its QR is usually too far away to scan.
• Under a lip or overhang. The phone has to lie flat against the face; a shelf edge two inches above it stops that.
• Two Markers within a hand's width. Both will read, and the visitor will not know which they got.
• A spot nobody stands. The best surface in the building is worthless if there is no reason to be in front of it.