What the rules allow
The Rules of Golf permit a player to obtain distance information during a round. That change was a significant liberalization — distance-measuring devices were once banned outright — and it's why rangefinders are now standard equipment in amateur golf.
What remains prohibited is using a device to measure or gauge conditions that might affect play, which includes elevation change and wind. That distinction is the whole issue.
Why slope is the problem
"Slope" on a rangefinder means it accounts for uphill and downhill. A flag 150 yards away but 20 feet above you plays longer than 150 — the device does that maths and gives you an adjusted number.
That's genuinely useful and it's also exactly what the rules prohibit in competition, because it's gauging a condition affecting play rather than simply measuring distance.
The slope switch
Manufacturers solved this with a physical, visible switch that disables slope. The key word is visible: a playing partner or a rules official has to be able to see at a glance that the feature is off.
On most models this is a sliding collar that changes the color of a band on the body, or a faceplate that swaps. It's deliberately obvious, and that's the point — a device where slope is disabled through a hidden menu doesn't satisfy the requirement in the same way.
The buying implication:if the recipient plays in club competitions, they need either a rangefinder with no slope at all, or one with a visible slope switch. This is the single most important spec to get right, and it's more important than brand, magnification or maximum range.
Local rules can vary
Individual competitions can adopt a Local Rule prohibiting distance-measuring devices entirely — this is used at elite level and occasionally at club level.
In practice, most club golf permits standard rangefinders. But the position varies by competition, so a golfer entering a specific event should check its conditions rather than assume.
What about GPS watches and apps?
The same principle applies. Distance information is fine; elevation adjustment and other condition-gauging features are not, in competition.
Most golf GPS devices have a competition or tournament mode that disables the non-conforming features. As with slope switches, the golfer is responsible for having it set correctly.
Casual golf
None of this applies to a social round. If the recipient plays for fun with friends and never enters a competition, slope is purely an upgrade and there's no reason to avoid it.
The reason we lead with the rules is that a rangefinder is an expensive gift, and buying a non-switchable slope model for someone who plays club competitions is a genuine miss. Our rangefinder guide notes which models have the switch.