The round blood'n' tar snelm is a member's only helmet. There are no requirements for wearing it. It can be obtained either by using the Crafting skill or trading with another player.
In level two clue scrolls, the conical form is called the 'pointed red and black snelm' and the round form is called the 'round red and black snelm'.
To make a blood'n' tar snelm the player needs at least 15 Crafting, a Blamish red shell (round), and a chisel. Creating a blood'n' tar snelm will give the player 32.5 Crafting experience regardless of the snelm type.