Everyone can play Knaster at the same time; all you need is a score sheet and ears to hear which number is being rolled on two dice.
Your score sheet has a 5×5 grid on it, along with numbers from 5-10 outside the rows, columns, and diagonals of this grid. On a turn, someone rolls the two dice, then calls out the sum. Each player either:
Writes this number in an empty space in their grid, or
Circles this number in their grid if it had been entered on any previous turn.
Initially, of course, you can only write a number as you have nothing to circle. You’re trying to do two things in Knaster: circle lots of numbers, and fill the rows, columns, and diagonals of your grid with "scoring combinations" of numbers, i.e., three- to five-of-a-kind, two pairs, a full house, or a straight. When you place five numbers in a row, column, or diagonal and you have created one of these scoring combinations, then you immediately circle 1-3 numbers in this same line. If all the numbers in a line are circled, you can then circle the number (5-10) outside the grid that’s next to this line.
As soon as someone fills in the 25th space in the grid, they let everyone know this, then after one final turn, the game ends. Your score is equal to the sum of the circled numbers outside your grid, along with 1 point for each number circled in your grid. Whoever has the highest score wins!