why players are putting fireplaces old school runscape?

[Super Girl]

first i joined a world then i see players lighting fireplaces on a line

here is a screenshot:

can please somebody answer

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sorry i did not mean to put a textbox on the screenshot

They are practicing their 'Firemaking' skill. When lighting logs, your character automatically moves to the next square after creating the fire. They are then lighting the next log from their inventory. It ends up creating a long line, sometimes.