the slider is the patio door that opens,if you are talking about anti lift blocks then they are screwed to the head(top) of your frame(not door),you can see them when door is open,unscrew these and take them out if it has them as not all do,but you have to lower the door by taking rubber gromets out of bottom edge of your slider(door that opens) then use screwdriver on the screws inside and turn anti clockwise untill door is low enough to lift out,you have to lower your door both sides or wont come out,feel free to send any pics if you still unsure through my website contact page,www.sdwupvcrepair.co.uk,hope this helps
shaun www.sdwupvcrepair.co.uk, August 2008
