Canvas sags over time, humidity changes, paint weight, and natural fiber relaxation gradually steal the drum-tight surface you need for controlled brushwork. Wood stretcher keys solve this. Tap these beveled wedges into the corner slots of your stretcher bars to incrementally expand the frame and restore proper tension. Masterpiece mills these keys from sustainably harvested California and Oregon wood, matching the quality of their stretcher bars.

Two thicknesses handle different needs: 1/8-inch keys provide subtle adjustments for maintaining canvas that's slightly loose, while 1/4-inch keys deliver the expansion needed when canvas has relaxed significantly or you're working with heavier fabric. The beveled design creates even pressure distribution as you drive them deeper, preventing sudden stress points that could tear canvas or crack paint layers. Keep extras on hand, keys get lost, and you'll want fresh ones when restretching older works. Proper canvas tension means your brushstrokes land where you intend them, with paint sitting on the surface rather than sinking into slack fabric.