a couple of 4 inch clamp or at least a bench hook
you can make a bench hook a piece off board or timber 12 to 25mm thick 250mm long by 150mm back to front
screw a piece of wood on the back top edge thats 18 to 25mm square idealy [but any batton will do as its to rest the wood against]make it 50mm shorter than the top length[250 -50= 200]
if your right handed line the batton up with the l/ h side so it stops short by 50mm on the right hand side
flip the wood over so the batton rests on the outside edge of your hard surface
fix an identical batton to the back edge of what is now the top again 50mm short on the r h side
once made you can use this for cutting timber against any hard surface
with the front batton hooked onto the front edge and the timber supported on the back batton
you can use a cloth to protect any surface that may be dammaged
when you saw you make shure you saw will cut down within the 50mm on the side
so theres you first hand made tool sorted
has any body said a work mate is realy handy
a metal framed mitre saw is ideal for strait or angled cuts for about £12 but needs checking as they are easily knocked out of square
you can also use your hand saw as a square and 45% angle as the handles are usualy set at the angles