Hi, I had to change the push pins which hold the straps on my seiko sportura watch.if you turn your watch face down,you will see the push pin in the gap between strap and main body, there is shoulder on the pin if you push shoulder into the strap this pop the pin out of main body.Be careful as the pin will spring out.it is very easy to do, putting strap back is the reverse.
Ian, November 2009