The full solution is below, with a short explanation for each group. To avoid spoilers, play the puzzle or open the hints page before reading the answer panels.
BELL, ALARM, CASHIER, and PHONE all fit the category "Things that ring". Each can make a ringing sound. The shared link accounts for all four words, which is why the remaining board words should be tested against a different rule.
Category
Map features
SCALE / COMPASS / BORDER / LEGEND
SCALE, COMPASS, BORDER, and LEGEND all fit the category "Map features". These help you read a map. The shared link accounts for all four words, which is why the remaining board words should be tested against a different rule.
Category
Things with lanes
ROAD / TRACK / BOWLING / POOL
ROAD, TRACK, BOWLING, and POOL all fit the category "Things with lanes". Movement is organized into lanes. The shared link accounts for all four words, which is why the remaining board words should be tested against a different rule.
Category
Things with keys
HOTEL / MAP / PIANO / LOCK
HOTEL, MAP, PIANO, and LOCK all fit the category "Things with keys". Each one can be associated with keys. The shared link accounts for all four words, which is why the remaining board words should be tested against a different rule.