and also, if you dont have means to get such really neat and realistic tools as these folks have mentioned above ...i give most of my work away so i'm alot tool poor and make due. my dumb but oh well!!!
if you are cutting with a 36" or longer straight edge...make sure that your table, counter or bench isn't pitted. then get your ass up on your table before you cut. make sure you've marked and set your leather right. before you cut, get your other hand, and your knee, and your foot on your steel edge. before you cut. make sure that you can cut this lenth that you now have secured under the steel. (or at least yer hand at top, knee in middle. if no foot, dont cut beyond your knee, leather might have resetteled under the loose end of the steel) re check your leather to make sure nothing moved. score the leather as smarter folks than i already said, dont gouge. this'll allow you to keep whatever yer cutting with at a staight angle instead of slicing sideways against the steel edge. reason for the knee, if youre not used to cutting long lenths of heavy or light oz, its inevetable you'll stretch or sqeeze your perfectly scored piece then it'll cut wrong. hey, its worked for me for 18 years now!