Anyone know how to keep cut square when hack sawing

[ACE HIGH]

and the all whites soccer team!!!!
And thanks for the tip shh20,which goes to show that we all learn from these forums,never tried the index finger tip re sawing but never to old to learn.David
Plus next time I am up north I have to face a high noon shoot off with slug guns (against targets!) against my new son in law and his Dad for a bottle of Tequila so will try that tip.I am "sort of" the defending champ but only because they still havent leaned to adjust their sites!!David