Determine the particular aspect of fifth-grade addition your model is teaching. For instance, focus a lesson on large-number addition or teach students how to add fractions.
Create a model for large-number addition by numbering building blocks with single digits from 0 to 9. Create one set of 10 blocks for each digit you plan to teach. If you are teaching addition of seven-digit numbers, use 14 sets of blocks. Students will turn the blocks to the appropriate side to create two rows of seven-digit numbers. Students can then use the blocks as a visual aid to help them solve the problem. Create sets for the largest numbers you plan on teaching; use fewer sets to represent smaller numbers.
Cut large blocks into smaller pieces with a jigsaw if your lesson plan deals with fractions. Leave at least one block intact to represent the number "1." Show students how various fractions add up to 1 or more than 1 by cutting other large blocks into halves, thirds and fourths. Students will manipulate the fraction models, such as combining blocks representing 1/2, 1/3 and 1/3. When they see the combination is larger than the block representing the "1," it will help them realize the three smaller pieces add up to a number greater than 1.
Create similar models for each addition lesson you plan to teach by using other items such as plastic cups or pieces of cardboard. For instance, a lesson on decimals could include a model of a cardboard circle divided into 10 equal parts, each colored with a different marker. Pennies or other counters could help students track each tenth.