RuneScape Classic Wiki
RuneScape Classic Wiki
The main RuneScape Wiki has an article on: Steel Throwing Dart
The Old School RuneScape Wiki also has an article on Steel Throwing Dart.

A Steel Throwing Dart is a throwing dart which can be obtained by smashing Strange Barrels or by attaching feathers to steel dart tips with level 37 fletching. Granting 1 fletching exp per dart created. It requires level 5 Ranged to equip.

Weapon poison can be used on them to create Poisoned Steel Throwing Darts.

Like all throwing darts, they provide no WeaponAim or WeaponPower, and when they are equipped, they are invisible to other players.