From the introduction:
Tunnel Quest or TQ for short, is a brief set of Fantasy Role-Playing rules, designed by Paul Elliot (of Zenobia fame) and developed further by Mike Hill (T&T Sixth Edition). The game was originally designed to create a simple but compelling set of rules that Paul could use with his family.
When the result of a character's action is in doubt, the Game Master (GM) asks for a dice roll to determine the outcome. The player rolls 2-dice and must get equal to or greater than the Difficulty Number. In a fight the Target Number is the Rating of the Foe. Most tasks can be rated in this way (climb portcullis might be 6). A Difficulty Number of 8 would be a typical challenge; 10 or more would be difficult and 13 or more would be formidable for starting characters, at any rate.
In many circumstances, the character may possess a Skill applicable to the situation; in which case, the player may add the Skill level to the dice roll.