if you look at the slats"on the bench, measure the lenght of them, and the width. see how their held on to the bench, are they bloted on? see if you can unscrew one of them off, you may have to cut one off with a hacksaw, dont matter you will be putting new bolts back on anyway,take the slat back to B&Q ect"with you , you can cut it in half if you want too, you just want to get wood the same in width,all you need to know is the length of your slats, if their 5 foot , just get a 6 foot length, and cut it to size, 5 foot,rember the harder the wood the longer it will last, but the more it will cost, best way is to take one of the slats with you, and ask for help in the shop, you will need a hacksaw a drill a screwdriver , to do this job, you need a drill to put holes in the slats for the "gutter bolts, that holds the slats on to the frame, just do one slat at a time when your doing this job, its not hard to do if you do it one slat at a time, oh you dont say what the lenght and width the slats are ?
k, March 2011