Almost every hardware problem on a site is a measurement that was not taken. Here is what to bring, by system type, so the answer takes one visit instead of three.
Load ratings in our catalogue: 2kg · 6kg · 10kg · 12kg · 14kg · 15kg · 20kg · 25kg · 30kg · 40kg · 50kg · 80kg · 120kg · 147kg
BRING: Cabinet internal width and depth, and what is going in the drawer
Runners are rated by load and by extension. A cutlery drawer is happy on the lowest rating in the range; a pull-out carrying steel vessels or a grinder is not. Partial extension leaves the back of a deep drawer unreachable, which is storage the client paid for and cannot use.
BRING: Finished door weight, door height and width, and the floor level across the run
Systems are rated per door. A tall shutter in mirror or lacquered glass gets heavy fast, and a system run over its rating goes stiff, then noisy, then off its track. Check the floor level along the whole run before ordering, because adjusters absorb a little and not a genuine slope.
BRING: Number of wings, door thickness, and whether it is inset or overlay
Wing count and door application change the whole gear set, not just the fixings. Getting inset against overlay wrong at order time means the doors do not sit flush and there is no adjustment that fixes it afterwards.
BRING: Door thickness, overlay, and the door weight
A solid timber shutter is far heavier than a flush shutter of the same size. Under-specified hinges let a door drop, and a dropped door stops latching and starts scraping the frame within a season.
BRING: Kitchen volume, hob width, and the duct route length and bend count
Every metre of duct and every bend eats airflow. A high-rated chimney on a long run with two right angles performs like a much smaller one. Size it against the route, not against the room alone.
BRING: Door thickness, backset, and the existing mortise pocket
Smart and mortise locks specify a thickness range and a backset. Three measurements decide the whole choice, and taking them at the door is two minutes against a wasted delivery.
A photograph of the elevation with dimensions on it is usually enough. WhatsApp it to the counter and you will get back a specification and a stock position, not a catalogue link.