The dozens (or columns) pays 2:1 so you have can create a longer progressive betting system than in bets that pay 1:1 - and at the same time cover a significant number (12).
Most players wait for a continued lack of numbers in a given dozen and bet on its reappearance. As the number that are covered are less than in the bets that pay 1:1, they usually wait for bigger trends of numbers absence.
For example, in the absence of numbers in the first dozen in the last 5 spins they start to a bet in the first dozen. For example, suppose you want to earn an additional profit margin close to $ 1 bet by using the Martingale system:
1 - Bet $ 1 - With a victory you win $ 2 - With a defeat you have a loss of of $ 1;
2 - Bet $1 - With a victory you win $ 2 (Profit = $ 1) - With a defeat you have a loss of $ 2;
3 - Bet $ 2 - With a victory you win $ 4 (Profit = $ 2) - With a defeat you have a loss of of $ 4;
4 - Betting $ 3 - With a victory you win $ 6 (Profit = $ 2) - With a defeat you have a loss of of $ 7;
5 - Bet $ 4 - With victories you win an $ 8 (Profit = $ 1) - With a defeat you have a loss of of $ 11.
6 - Bet $ 6 - With a victory you win $ 12 (Profit = $ 1) With a defeat you have a loss of of $ 17.
7 - Bet $ 9 - With a victory you win $ 18 (Profit = $ 1) - With losses you have a loss of of $ 35.
8 - Bet $ 18 - With a victory you win $ 36 (Profit = $ 1) - With a defeat you have a loss of of $ 71.
9 - Bet $ 36 - With a victory you win $ 72 (Profit = $ 1) - With a defeat accumulate - $ 143.
10 - Bet $ 72 - With a victory you win $ 144 (Profit = $ 1).
You can also bet simultaneously two dozen to cover 24 numbers. However, two dozen bet through a betting system progressive the values in a bet can go up very quickly ..
Betting on the columns or on the dozens is the same, although most players prefer the dozen since is easier to interpret.
