The Spear & Jakson grass trimmer from Argos can be dismantled and you will need a 30mtr cutting line to replace existing.
Remove cutting gard, undue the locking screw( this will be tight and a pair of grips will be needed) remove locking srew philips.
Undue allen key bolt holding body of strimming head, pull head off. The bottom plastic bump screw can be unwound once the bottom cable holder has released from the top.
Once unscrewed undo line and replace with new, re-assemble as removed, the cost of a line is less than £10 to replace from spares £20.
dm, February 2010